OGRAPHY 



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ENGINEER COURSE 

IN 

TOPOGRAPHY 



THE GENERAL SERVICE SCHOOLS 

FORT LEAVENWORTH, KANSAS 

1921-22 




THE GENERAL SERVICE SCHOOLS PRESS 

Fort Leavenworth, Kansas 

6-20-22— 2M 



1922 






LI3RARY OF CONGRESS 

RECEIVES 

. OCT 9 1923 

DOCUMENTS D1V1&ION 



PREFACE 

This pamphlet has been prepared by the Engineer Sub- 
section with the object of presenting in convenient form 
the data necessary for the course in Topography at The 
General Service Schools. The material has been obtained 
from other army publications and from lectures and con- 
ferences prepared by the engineer instructors during the 
courses of 1919-1920-1921. 

The course in Topography at The 'General Service 
Schools is not a course of instruction in methods of topo- 
graphy, but is a course of application of topographical 
methods to the military art. This pamphlet is printed in 
limited numbers for use as a text at The General Service 
Schools. 

H. A. Drum, 

Assistant Commandant. 
Approved : 

H. E. Ely, 

Commandant. 



TABLE OF CONTENTS 

Chapter I— INTRODUCTION: equipment needed; measured course 
for determining length of stride; model scale for alidade. 

Chapter II — MAP READING: title; co-ordinates; scales; compass; 
contours; shelter from artillery fire; orientation; aeroplane pho- 
tographs; practical exercises. 

Chapter III— USE OF INSTRUMENTS: methods; standard sketch- 
ing equipment; azimuths; distances; elevations; slope equivalent; 
details of making a sketch; indoor exercises in use of instruments; 
practical exercises. 

Chapter IV— APPLIED MILITARY SKETCHING: road sketch, 
railroad, stream, woods, camp, outpost, place, landscape; combined 
sketching; rates of sketching; data; practical exercises. 

Chapter V— AIRPLANE MAPPING: present state of development; 
statement of uses of airplane photographs; advantages and limi- 
tations; use in reconnaissance and mapping large areas; battle 
maps; general maps; interpretation and restitution; interpreta- 
tion of enemy works. 

Chapter VI— MAPPING LARGE AREAS: United States mapping or- 
ganizations; present status as to maps; grid system in United 
States; system of mapping large areas; system for United States 
Army; organization for 10,000 square miles per month; assistance 
by aeroplanes. 

Chapter VII— MAP REPRODUCTION: Classification of methods; de- 
scription, blue print, brown print, neo-cyclostyle, Ellam duplicator, 
hectograph, Dorel process, lithography; reproduction outfit with 
division, corps, army, general headquarters; mobile plant; A. E. 
F. results, 1st Army, 2d Army, general headquarters; assistance 
by staff officers; issue schedule of maps for A. E. F. infantry divi- 
sion; summary of work done by base plant at general headquar- 
ters. 



CHAPTER I 

Introduction 



1. The following equipment will be needed for the 
work in topography : 

Colored and black pencils Buy from Book Dept. 

Erasers 

Leavenworth 3" sheet 

Gettysburg 3" sheet 

Alidade " " 

Pace tally " " 

Celluloid sheets " " 

Hand level or clinometer — Issued from instrument room on memoran- 
dum receipt. 

Sketching case — Issued from instrument room on memorandum re- 
ceipt. 

W. D. Pamphlet of Conventional Signs — To be drawn from Library. 

G. S. S. Pamphlet on Conventional Signs — To be drawn from Library. 

Paper protractor Issued from instrument room. 

Co-ordinate scale Issued from instrument room. 

Three-inch scale of meters, yards and miles__ Issued from instrument 
room. 

Celluloid paper should always be available for work in 
field in case of rain. This work proceeds in all kinds of 
weather, and celluloid paper is not injured by the rain. 

2. The following equipment should always be brought 
to lectures and conferences in topography : 

Colored and black pencils. 

Erasers. 

Leavenworth sheet 3" map. 

Gettysburg sheet 3" map. 

Alidade. 

Sketching board. 

Pamphlets on Conventional Signs. 

This pamphlet. 

Protractor. 

Co-ordinate scale. 

Three-inch scale of meters, yards and miles. 

It is advisable to form the habit of bringing the tripod 
with the sketching case, as otherwise it may be forgotten 
later when there is field work. 

l 



2 TOPOGRAPHY 

3. The following distances have been measured along 
Grant Avenue for use in determining length of stride : 

Beginning on the west walk of Grant Avenue on a line 
with the south side of the converter station (small building 
south of Post Exchange), thence south to southwest wing 
of arch bridge over Corral Creek. Distance from begin- 
ning, 6,009 feet. 

Thence south to southwest corner of Grant and Metro- 
politan Avenue (curb at former saloon) . Distance from be- 
ginning 8,750 feet. 

This entire course should be paced down and back by 
members of the class to determine the length of stride to 
be used in the sketching work. 

It is necessary that this pacing be done so that the 
length of stride is known before the beginning of field work. 

After the length of stride has been determined, it will 
be necessary to obtain from the instrument room an alidade 
and a ruled scale corresponding to the length of stride. This 
ruled scale will be pasted on the alidade. 

4. For rapid work the differences of elevation for one 
degree of slope for the distances given should be shown on 
each side of the alidade. To obtain the total difference of 
elevation with any degree of slope for a fixed distance, mul- 
tiply the number of degrees by the difference of slope for 
1 degree marked on the same line as the distance. 

5. The three drawings herewith show the usual scales 
on the three sides of the alidade. 



CHAPTER II 

Map Reading 



1. Each complete map, in addition to the map proper, 
should show all the information necessary for map reading. 
On a finished map this generally consists of the following : 

(1) The title, consisting of : 

(a) Name of organization under whose auspices it is made, 

as Corps of Engineers, U. S. Army; 8th Corps Area; 
1st Division; etc. 

(b) A statement showing what the map represents, i.e., its 

'particular feature or purpose, if any, as position sketch. 

(c) The locality. (This and the preceding item may be in- 

terchanged.) 

(d) Its sources, as surveyed by, etc.; compiled from, etc.; 

reduced from, etc. 

(e) Under whose direction, if any. 

(f) By whom. 

(g) The date. 

(h) Linear scale, generally in inches to the mile. 

(i) Representative fraction. 

(j) Graphic scale, generally in miles or thousands of yards 

and fractional parts thereof, 
(k) Contour interval. 
(1) Scale of slope equivalents (frequently omitted). 

(2) Notes showing: 

(a) Reference or datum plane for elevations. 

(b) Miscellaneous. 

(3) Arrows showing true and magnetic azimuth, and 
magnetic declination. 

(4) Legend, if necessary. 

(5) Latitude and longitude of projection lines. 

(6) A key map showing other sheets, if map is one of 
a series of sheets; or references in margins to adjacent 
sheets of such a series. 

Plate II shows a specimen title suitable for military 
sketching. The title should, when practicable, be placed in 
the lower right hand corner. 



MAP READING 5 

1ST DIVISION 
Position Sketch 

Of Area 
northwest of 

Fort 5 am Houston, Texas 
Showing Sector of '2d Brigade 
by 

Capf. A 1st Inf 

February 21,1920 

Scale: 6=1 mile R.Fi:i0-S6O 

lOO 50 O lOO 200 SOO AOO 500 Yards 

i.ii 1 1 ■ 1 1 1 r i _i i i i 

V. I.-IOFr: 
1 L! I ?! I 3' ,f,5-,6-,7-|OX 

Note :- Elevations are above mean see level, 

based on (J 3 Geological Survey data . 

Plate II 

2. The following suggestions will be of assistance in 
map reading: 

(a) Note the title, purpose, kind (sketch, survey, etc.), 
authorship, and date of the map, with a view to estimating 
its probable accuracy and usefulness for your particular 
purpose. 

(b) Note the meridian on the map and associate it 
with the local meridian. 

Note the declination of the compass, and the relations 
between the true meridian and the grid lines if any. 

(c) Note the scale of the map (see par. 12). If only 
the R. F. is given, the number of inches to the mile may be 
calculated by dividing 63,360 by the denominator of the 
R. F. ; thus, if the R. F. is 1 : 80,000, then the scale in inches 
to the mile is 63,360 :80,000, or 0.792 inches to the mile. 

If there is no scale, look for some other indication of 
distance. It may possibly be found in local names, as Three 
Mile Creek, Two Mile House, etc.; in roads uniformly 
spaced; in city blocks, which are usually about 100 yards 
on the shorter side; railroad stations or sidings, the dis- 
tances apart of which may be taken from time tables; in 
the spacing of co-ordinate grid lines; in the spacing of 



6 TOPOGRAPHY 

parallels of latitude (assume roughly 69 miles to each de- 
gree, or 1.15 miles to each minute of latitude). 

(d) If the map is contoured, note the contour intervals 
and the scale of slope equivalents. If the contours are not 
numbered, decide which are the high and which the low 
ones. Closed contours are much more likely to be elevations 
than depressions, especially if several are concentric. If the 
contour interval is not given, it will be difficult to get any 
clue to it unless isolated elevations appear on the map. If 
the ground is accessible, the contour interval may be de- 
termined by actual measurement of gradient. 

(e) Note all topographical and cultural signs and asso- 
ciate them in mind with the advantages or disadvantages 
for military operation. Note the legend, if any. 

(f ) Note the system of co-ordinate grids if any — the 
spacing of the grid lines, the co-ordinate numbers, and 
whether meters or yards are used. If the map is not 
gridded, but is provided with meridians and parallels of 
latitude, points may still be definitely located by stating 
their positions with reference to these meridian and latitude 
lines. 

3. The study of a map is much facilitated by the use 
of a relief map, or of photographs made from relief maps. 
Relief maps also furnish a quick and easy (but somewhat 
approximate) means of solving visibility problems, by the 
use of a minute electric lamp. The lighted and shaded 
areas show at once what terrain is visible from the point 
at which the lamp is located. The best way to study a map 
is by work with the map, on the ground. 

4. Co-ordinates : — The system of co-ordinates adopted 
at these schools is based on squares 1,000 yards to a side. 
There are two groups of maps in general use, viz., the 
Leavenworth Group and the Gettysburg Group. In the 
Leavenworth Group, the lines 350 and 750 run through 
the school tower. In the Gettysburg Group, the lines 350 
and 750 run through the Gettysburg Central Square. The 
origin of these co-ordinates is not defined, but it is taken 
somewhere to the south and west of the mapped area so 
that all co-ordinates will be positive in sign. The French 



MAP READING 7 

before the war used Treves, Germany, as an origin, but in 
order to avoid negative readings, changed to an indefinite 
point 500 kilometers to the west and 300 kilometers to the 
south. 

5. All maps used for problems in these schools are di- 
vided into squares, one thousand yards on a side on the 3- 
inch maps and five thousand yards on a side on the 1-inch 
maps. Lines creating this division are numbered succes- 
sively from left to right and from bottom to top. These 
lines form the basis for the system of co-ordinates. 

Briefly stated, the system of co-ordinates is used to 
find the location of a point by co-ordinates expressed in 
thousands of yards, dropping off the figures not necessary 
for accuracy, and then writing the figures beside each other, 
properly pointed off, X co-ordinate first, the two co-ordi- 
nates being separated by a .dash. A number of pairs of 
co-ordinates written one after another would be set apart 
by commas between the pairs. 

The following example will illustrate the above: 
The co-ordinates of a certain point to three decimal 
places are: 

X = 197.783 

Y = 262.724 

For ordinary purposes, locations to closer than the 
nearest 100 yards (tenth of a thousand yards) are unneces- 
sary. Consequently for ordinary purposes, the co-ordinates 
of the point are expressed thus : 

X= 197.8 

Y = 262.7 

The methods of writing the above point as required at 
this school are 197.8—262.7 for 1", 2", 3", 4", 6" map. 

The 12" map is supposed to represent the ground itself, 
thereby giving reality to indoor problems requiring the use 
of the terrain. It, therefore, has no co-ordinate grid 
printed on it, as the ground has no co-ordinates. 

6. In work requiring their constant use co-ordinates 
are frequently abbreviated, when there can be no confusion 



% TOPOGRAPHY 

as to general location, by omitting the tens and hundreds. 
Thus, point (197.8—262.7) may be written point 78.27. 
This method of abbreviation is in general use by the Field 
Artillery. In all work at these schools co-ordinates are re- 
quired to be written out in full. 

7. In designating a line of co-ordinates, the co-ordinates 
of sal; en t points in the line should be written one after 
another, separated by commas, thus, line 358.7 — 761.2, 
358.9—761.6, 359.2—761.9, 359.6—762.4, 360.4—762.9. A 
square may be designated by the word "square" followed by 
the co-ordinates of its southwest corner with the decimals 
omitted, thus: "square 342 — 7-U." 

8. Conventional Signs: — For the purposes of this 
course, conventional signs will be used as indicated in the 
War Department pamphlet Conventional Signs, United 
States Army Maps. This is the only official pamphlet on 
the subject. As it does not give all the signs which will be 
needed for this course, the pamphlet of special signs issued 
here will be used until such time as another War Department 
publication designates conventional signs to cover the school 
requirements. 

9. In military mapping, and particularly in field 
sketching, the exclusive use of conventional signs is fre- 
quently impracticable, and a written designation or descrip- 
tion by words is often more intelligible and more quickly 
recorded. These verbal designations or descriptions are 
often cause of much confusion due to their indefinite char- 
acter; where conventional signs are prescribed they should 
be used. 

10. A method of expediting sketching is seen on many 
maps, viz., to surround an area with a narrow border of the 
proper sign and leave the middle blank. The pamphlet of 
conventional signs shows special signs which are often used 
for rapid sketching work. 

11. Scales: — All maps are drawn to scale; that is to 
say, one unit of length on the map always represents a cer- 
tain number of the same units on the ground. This scale 
may be represented on the map in one or more of three 
ways: 



MAP READING 9 

(a) By words, as 3 inches = 1 mile. This system is followed 
in the United States and in practically all parts of Great Britain. 

(b) By a ratio shown as the representative fraction (ab- 
breviated R. F.), which gives the ratio of a unit of length on the 
map to a similar unit on the ground. For example, the R. F. of 
a l"-to-the-mile map is 1:63,360, since 1" on the map equals 1 mile 
on the ground, or 63,360 inches. The R. F. is the only method 
of giving the scale which will permit it to be understood by all 
peoples, regardless of their unit of length. 

(c) By a graphical scale, usually given on American and 
English maps in miles or thousands of yards and fractions thereof. 
Other nations use kilometers and fractional parts. An impor- 
tant advantage of a graphical scale is that in case the map has 
been reduced or enlarged from another map the scale is still true, 
which is not the case for the other methods of representing the 
scale. 

12. Scales of Standard Maps: — The map scales 
adopted as standard for use by the military forces of the 
United States are as follows: 

1:20,000 (approximately 3 inches=:l mile), fire control map, 
or training map, for detailed trenches, enemy organization, artil- 
lery objectives. Limited areas only will be covered on this scale. 

1:62,500 (approximately 1 inch = l mile, tactical map, for 
general use in open warfare. 

1:250,000 (approximately 1 inch = 4 miles), strategic map, 
for general study of theater of operations, supply system. 

1:500,000 (approximately 1 inch = 8 miles), general map. 

1:1,000,000 (approximately 1 inch = 16 miles), general map~ 

1:2,500,000 (approximately 1 inch = 40 miles), geographical', 
map of the U. S. 

1:7,000,000 (approximately 1 inch = 110 miles), geographvcat 
map of the U. S. 

13. Scale of Special Maps: — The use of maps of 
scales larger than 1 :20,000 for general military purposes 
is to be discouraged, and such maps will not be used in 
training unless specially authorized by the War Department. 
When, however, for special purposes it becomes necessary 
to show detail which cannot be shown on maps to 1 :20,000 
scale, either 1 :10,000 or 1 :5,000 may be used. Except for 
some engineering and construction purposes, maps of scale 
larger than 1 :5,000 will rarely, if ever, be needed by the 
military forces. In general, the various scales will be used 
as follows : 

(a) 1:62,500. — For route maps of extended marches, or of 
marches of large commands using several roads. 

(b) 1:20,000. — For ordinary route sketches and extended 
marches, or of marches of large commands using several roads. 

(c) 1:10,000. — For position and outpost sketches. 

(d) 1:5000. — For maps used in the war game, discussion of, 
operations at maneuvers, and in siege operations. 



10 TOPOGRAPHY 

14. The scales heretofore most commonly used for mili- 
tary sketching are as follows : 

3" = 1 mile, for mounted sketching or route sketches in gen- 
eral. 

6" = 1 mile, for area, position, outpost or other sketches made 
on foot. 

12" = 1 mile may be used when greater detail is required. 

While the above scales differ from those adopted for 
War Department maps they will still continue to be used 
until it is possible to replace them. 

15. It is not practicable to have prepared under War 
Department supervision, in the field, all the maps required 
for military use, and consequently the maps of some of the 
several civil agencies of the Government engaged upon sur- 
vey work have been adopted as standard for such use. 

16. A.R. No. 100-15, 1920, which covers the subject of 
maps and map making, classifies maps for use of the mili- 
tary forces as Standard and Special. 

Standard maps are those which, whether geographic 
or topographic in character, are ordinarily made in time of 
peace, as an element of preparedness, or for the commercial 
development of the country. They are printed in quantity 
for general uses. 

Special maps are those especially made for special pur- 
poses. The purpose ordinarily is to show, as to a particular 
area, certain details not found on standard maps thereof. 
Special maps may be topographic maps to special scales, 
or may be produced by drawing or printing on standard 
maps, the data desired to be made available. 



map reading 11 

17. Table of Map Scales Used by Various Nations : 





i* 

00 


i* 




R. F. 


l"Sa 




Country 




- =~ 


~ ~ ^ 








R,S g 








<*"S^ 




1 '5000 


12 


1-12 




1 10,000 


6 


1-6 




1 20,000 


3 


1-3 


United States 


1/62.500 


1 


1 




1 125,000 


1-2 


2 




1 250,000 


1-4 


4 




1 6,000,000 


1-16 


16 




1/5,000 


12 


1-12 


• 


1 10,000 


6 


1-6 




1/20,000 


3 


1-3 




1/50,000 


1 1-4 


4-5 


France 


1 80,000 


4-5 


1 1-4 




1/100,000 


3-5 


1 3-5 




1/200,000 


1-3 


3 




1/320,000 


1-5 


5 




1 500 000 


1-8 


8 




1/600,000 


1-10 


10 




1/1,000,000 


1-16 


16 




1/10,000 


6 


1-6 




1/31,680 


2 


1-2 


Great Britain (does not 


1 63,360 


1 


1 


include maps they 


1/125,000 


1-2 


2 


used in France and 


1 253,440 


1-4 


4 


Belgium) 


1/1,000,000 


1-16 


16 




1 25.000 


2 1-2 


2-5 




1/100,000 


3-5 


1 3-5 


Germany 


1 200,000 


1-3 


3 


(not complete) 


1 1.000,000 


1-16 


16 




1/20,000 


3 


1-3 


Japan 


1 100,000 


3-5 


1 3,-5 


(not complete) 


1 100.000 


3-5 


1 3-5 


Mexico (maps of Mex- 


1/4,530,000 


1-72 


72 


ico are inaccurate) 



18. U.S. Geological Survey sheets are generally 1 :62,- 
500 (about 1"=1 mile) and 1:125,000 (about \"=1 mile). 
The 1 : 62,500 sheets cover 15' of latitude and 15' of longi- 
tude. 

For the Progressive Military Map, the United States, 
Portq Rico, and Hawaii have been divided into a series of 
numbered sheets, the highest number being 825. Each sheet 
is divided into 8 sub-sheets, thus : 

N— I, N— II, N— III, N— IV, 
S— I, S— II, S— III, S— IV. 

Most of these sub-sheets are drawn to a scale 1 :62,500 
covering 30 minutes of longitude and 15 minutes of lati- 
tude. 



12 TOPOGRAPHY 

19. The correct designation of maps now used in prob- 
lems, conferences, etc., at these schools is given below : 

General Map, Gettysburg-Antietam, 1" = 10 miles. 

General Map, Gettysburg-Antietam, 1" = 5 miles. 

Gettysburg-Antietam Map, 1:21120; sheets are designated by 
name as "Taneytown sheet." 

Gettysburg-Antietam Map, 1:5280; sheets are designated by 
letter and number as Sheet A-5. 

Pennsylvania and Maryland Geological Survey Map, 1:62500; 
sheets are called "Taneytown quadrangle," etc. (Two states in 
name as boundary crosses the quadrangle.) 

General Map, vicinity of Leavenworth, 1"=15 miles. 

Map of Fort Leavenworth and Vicinity, 1:21120; sheets are 
designated by name, as "Boling sheet," etc. 

Map of Fort Leavenworth and Vicinity, 1:5280; sheets are 
designated by letter and number, as sheet E-3. 

Kansas-Missouri Geological Survey Map, 1:62500. There 
are four separate sheets called: Leavenworth and Vicinity; 
Leavenworth Quadrangle; Smithville Quadrangle; Platte County, 
Missouri. 

Geological Survey Map, Leavenworth and Vicinity, printed 
in black, 1:62500. 

Kansas-Missouri special, printed in black, 1:62500. 

Road Map of Fort Leavenworth, Kansas, and Vicinity, 
1:62500. 

Road Map of Easton, Kansas, and Vicinity, 1:62500. 

Map of Part of Kansas and Missouri, Geological Survey, 
printed in black, 1:125000. 

For example, the following might appear at the begin- 
ning of a problem : 

MAPS: Gettysburg-Antietam Map 1:21120, Taneytown, 
Kingsdale, Bonneauville, Gettysburg sheets. 

20. Compass : — The compass does not point to the north 
pole. It points to the magnetic pole, which is in the northern 
part of British America (Canada) . However, along a mean- 
dering line running near Charlestown, Cincinnati, and Sault 
Ste. Marie, the compass points to the north pole, while 
pointing at the same time to the magnetic pole. East of 
this line the compass points west of true north ; west of the 
line the compass points east of true north. 

The following should be remembered : The direction 
of an object, expressed in degrees from the north measured 
round to 360° with the hands of a watch, is the azimuth of 
the object. As there are two norths used, true and mag- 
netic, there are two azimuths used, called true and magnetic 
azimuths. In military work the azimuths alivays, unless 
otherwise stated, refer to true azimuths, that is, to the azi- 
muths measured from true north. 



MAP READING 13 

21. A knowledge of the peculiarities of the compass is 
necessary to map reading. At Fort Leavenworth, if you 
are ordered, while in the field to change the direction of your 
advancing line so that it will move in the direction 37° 54', 
you do not advance in the compass direction 37° 54'. You 
remember that the order refers to map north (that is, true 
north) and that the magnetic declination at Fort Leaven- 
worth is 9° east; you subtract 9° from 37° 54' and advance 
in the magnetic direction 28° 54'. In other words, in this 
longitude, you subtract the magnetic declination from the 
true north in order to get the compass reading; and vice 
versa, you add the magnetic declination to the compass read- 
ing to get the true north. In Europe you do just the oppo- 
site. 

22. The following rules are easy to remember : 
First, west of the line of no magnetic declination (as 

at Leavenworth), where declinations are east: 

(a) Add to the magnetic, to get the true. 

(b) Subtract from the true, to get the magnetic. 

Second, east of line of no magnetic declination (as at 
Gettysburg and in Europe), where declinations are west, 
do just the opposite, viz. : 

(a) Subtract from the magnetic, to get the true. 

(b) Add to the true to get the magnetic. 

Verify these rules from a sketch or mental picture. 

23. The mean magnetic declination for any map can 
usually be found indicated on the sheet. A common method 
of indicating it is to draw an arrow with a full arrowhead 
pointing to true north, another arrow pointing to magnetic 
north with half a head drawn on the right or left hand, 
according as the declination is east or west, and to in- 
scribe the declination either in the space between the lines 
or on the magnetic meridian. This declination changes 
from year to year, but the declination marked on the map 
is accurate enough for all practical purposes. 

24. Contours: — The best way to learn to read con- 
tours, and later to draw them, is to practice the drawing of 
contours on a sketch where the critical points are given 
and with the actual ground in sight. By this means, one 
learns just what are the critical points, how they should be 
selected in the field and how a failure to properly select 



14 TOPOGRAPHY 

them will lead to a false representation of the ground, how 
to read at a glance differences of elevation, and how in 
sketching to draw in the contours by looking at the ground 
itself. 

25. The War Department is the only organization 
which appears to have adopted any logical scheme of con- 
tours ; foreign maps and Geological Survey maps have cer- 
tain contours to certain maps, but they represent no fixed 
scheme of slopes for different maps. Of course they rep- 
resent difference of elevation, but a glance at foreign con- 
toured maps does not show, without calculation, the slope of 
the ground. On the other hand, the War Department maps 
have a fixed relation of contours so that the number of 
contours shows the slope, regardless of the scale of the 
map. Thus for the 3" map, we have 20-foot contours 
(3X20=60) ; for the 6" map, we have 10-foot contours 
(6X10=60), that is, twice as many contours for the same 
difference of elevation ; but as the 6" map has twice the lin- 
eal dimensions of the 3" map covering the same territory, we 
have the same number of contours for the same lineal dis- 
tance on the paper ; for the 12" map we have 5-foot contours 
(12x5=60), that is, four times as many contours for the 
same difference of elevation, but as the lineal dimensions 
of the map are four times as great as on 3" map for the 
same territory, we have the same number of contours for 
the same distance on the paper. For the War Department 
maps the following contour intervals are prescribed: 

Feet 

1/62,500, vertical interval, normally 20 

1/20,000, vertical interval 20 

1/10,000, vertical interval 10 

1/5,000, vertical interval 5 

Consequently with War Department maps, except the 
20-ft. contour, 1 : 62500 maps, anyone can know at a glance, 
without reading the contour intervals, whether the ground 
is very steep or rolling or flat, but for exact differences of 
elevation he must look at the contours. In some foreign 
maps, hachures show the character of the slope, and the 
hill tops have elevations, but this method obscures the map 
and lacks the exactness of that of contours. 

With a contoured map it may help in map reading to 
take a colored pencil, and trace the important contours. 



MAP READING 15 

Also it may help if the map is shaded, grading from white 
on the level to darkest on the steepest slopes. 

26. The critical points of a terrain are in the stream 
lines and the ridge lines; for at those points the contours 
change their direction most rapidly. A few critical points 
with known elevations along stream lines and on ridge lines 
are of more value in drawing contours than are a greater 
number of points not critical. 

27. Figure T-l shows a map with the critical points 
marked and the elevations shown. The problem is to draw 
contours at 10 feet vertical intervals, with no other data 
than that given. The first step is to locate the points where 
desired contours cross the main stream line. As there are 
no falls between elevation 790 and elevation 850, it is as- 
sumed that the slope of the stream between these points 
is nearly uniform, becoming, however, a little steeper as the 
stream is ascended. Under this assumption the crossing 
points of contours 800, 810, 820, 830, and 840 are at once 
interpolated by eye on the main stream between 790 and 
850. By interpolation between these,, the elevations of 
the points where each of the tributary ravines enter the 
main stream are secured. Between these latter points and 
the heads of the ravines, the elevations of which are given, 
the points where the contours cross each of the ravines 
are marked. 

28. Each point shown along the ridge lines was chosen 
as being a critical point, that is, a point where the slope 
or direction of the ridge changes. From point to point 
along the ridge lines, it is assumed that the slope is uni- 
form. The points where the intervening contours cross 
the ridge lines have, therefore, been interpolated. The re- 
sult of interpolation along stream and ridge lines is shown 
in Figure T-2. As a rule, the ridges and spurs of eroded 
hills point in the general direction of the junctions of the 
streams which have eroded them. Therefore, interpola- 
tions have been made in these directions. 

29. The contours are now drawn in by joining the 
arrowheads in streams with the corresponding elevation 
on the ridge lines. See Figures T-2, T-3, and T-4 for the 
successive steps. 



16 topography 

30. Characteristics of Contours. 

(1) All points on any one contour have the same elevation. 
A contour is a level line. 

(2) Every contour closes on itself, either within or beyond 
the limits of the map. In the latter case the ends of the con- 
tour line will run to the edge of the map. 

(3) A contour which closes within the limits of the map in- 
dicates either a summit or a depression. In a depression there will 
usually be found a pond or a lake. If there is no water, the 
depression must be indicated in some way to differentiate it 
from a summit. The usual method is to hachure the inner side 
of the depression contour. 

(4) Contours never split and never cross each other except 
in the case of an overhanging cliff, in which case there must 
be two distinct intersections. These cases are not common. 

(5) Contours are spaced equally to represent a uniform slope. 
If the slope is a plane surface (i.e., if it has no irregularities 
due to erosion or other cause) the contours are parallel and 
straight. 

(6) In crossing a valley the contours run up the valley on 
one side; turning at the stream, run back on the other side. In 
crossing a ridge the contours run to the ridge line and, turning, 
run back on the other side of the ridge. 

(7) Contours are always at right angles to the lines of 
steepest slope. They, therefore, cross the stream lines and the 
ridge lines at right angles. 

(8) The contours are farther apart at the top and bottom 
of an eroded hill than near the middle, because in these portions 
the slope is somewhat flatter. 

(9) Contours are usually closer together near the sources of 
streams — as a stream is usually steeper near its source. This 
is not always so. A stream may have at its source a very flat 
collecting basin, a lake, or pond. 

(10) The smaller the stream, the steeper the slope in the 
usual case. Hence, contours are usually closer together on tri- 
butaries than on main streams. 

(11) Bad shaping of contours is usually due to illogical in- 
terpolation between critical points. The drainage lines and ridge 
lines are master lines of contours. Interpolate along the drain- 
age lines first, beginning on the main lines and going to the 
tributaries. Then search out the ridge lines and interpolate along 
the lines of the ridges. 

(12) If one has difficulty in tracing out a particular contour, 
he may be helped by imagining himself to be walking along the 
contour. If he starts out with low land on his right hand, he 
will always have low land on his sight hand as long as he walks 
that contour in that direction, and vice versa. 

31. Figure T-5 shows an attempt at contouring, where- 
in each of the above characteristics are violated. 

Each number on the figure show the particular charac- 
teristic which has been violated at that point. 

1-1 shows the same contour crossing the same stream 
twice; this is impossible. 

2 shows a contour ending within the limits of the 
map ; it cannot be done. 



MAP READING 



17 



3 shows a closed contour within the limits of the map. 
Evidently, it is a depression contour, but there is nothing 
to show that it is of a different nature from any of the 
other closed contours, all of which represent tops of hills. 

4 shows a contour which splits ; this is unreasonable 
because there is no overhanging cliff and there is only one 
such intersection or split. 

5-5 shows unequal spacing and hence unequal slope, but 
it is probable that the slope here is not unequal. 

6-5 shows contours going straight across a small valley ; 
no such valleys exist. 6a indicates that a man could walk 
straight from one stream to another on a level line ; such 
conditions never exist. 

7 shows a contour not at right angle to steepest slope. 

8-8-8 shows contours closer together at top and bottom 
of a ridge ; this is possible but not probable. 

9-9-9 shows contours closer together at the mouth of 
the stream; this is possible, but not probable. 

10-10-10 shows that the larger stream has the greater 
slope, which is not probable. 

11-11 shows bad shaping of contours due to illogical 
interpolation between critical points. 

12-12 shows the same contour twice on the same slope. 
This means that a man could walk to the right, continue 
along the contour, and then come back above his original 
position and still be on the same level. 

32. Figures T-6 to T-12 are critical points for sketches. 
It is advisable to practice on these figures so as to secure 
facility in drawing contours and in understanding the mean- 
ing of contours. 

33. Shelter from Artillery Fire: — The following 
table shows in round numbers the angle of fall of 75-mm. 
projectiles for different ranges. 





Shell 


Shrapnel 




Range in meters 


Approx. 


Approx. 






angle of jail 


angle of fall 




1.000 


2° 


2" 




2,000 


4° 


4° 




3.000 


8° 


7" 




4,000 


13° 


12° 




5.000 


20° 


17° 




6.000 


27° 


24° 




7.000 


37° 


32° 




8.000 


51° 


41° 





18 



TOPOGRAPHY 



By means of the above tables problems may be worked 
out showing whether certain positions are protected by the 
conformation of the ground from fire of 75-mm. guns. This 
table will be referred to in problems. 

34. The following table shows the relation between 
vertical and horizontal distances for slopes mentioned in 
above table. 



Slope in 
degrees 



2 


29 


horizontal to 


4 


14 


horizontal to 


8 


7.1 


horizontal to 


9 


6.3 


horizontal to 


11 


5.3 


horizontal to 


13 


4.5 


horizontal to 


16 


3.5 


horizontal to 


20 


2.7 


horizontal to 


26 


2.0 


horizontal to 


29 


1.8 


horizontal to 


33 


1.55 


horizontal to 


87 


1.35 


horizontal to 


39 


1.25 


horizontal to 


40 


1.2 


horizontal to 


46 


1. 


horizontal to 


50 


1. 


horizontal to 


51 


1. 


horizontal to 



vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
vertical 
1.04 vertical 
1.2 vertical 
1.25 vertical 



35. The following rule of thumb for converting degrees 
of slope to per cent of slope is fairly accurate up to ten 
degrees : 

Multiply degrees by % to get per cent. 

36. Visibility : — A problem frequently arising in map 
reading is that of determining what points are visible from 
a given point. 

The simplest and most satisfactory method consists in 
drawing a profile of the surface of the ground between the 
two points and then drawing the line of sight. If it touches 
any point of the surface as shown by the profile, the two 
points are not mutually visible. 

However, this method is long and tedious. A compari- 
son of the gradients between the two points and between one 
of them, lower most convenient, and intermediate points 
higher than the lower point is the method employed. A 
gradient to an intermediate point from the lower point 
steeper than the gradient between the two points under in- 
vestigation will mean non-visibility. Generally it is possible 
by inspection of the map to find two or three intermediate 
obstacles whose elevations are the deciding factors as to the 



MAP READING 19 

miftual visibility or non-visibility of the two points. Then, 
simple calculations will show in every case whether the two 
points are mutually visible. 1st: take the higher point, find 
its distance from the lower point, divide this by its eleva- 
tion above the lower point. 2d: take the higher point and 
each of the obstacles in turn, find the distance from the 
higher point to each obstacle, divide this by the elevation of 
the higher point above the obstacle. If the quotient of the 
1st (distance between higher and lower points divided by 
the difference of elevation) is in every case greater than the 
quotient of the 2d (distance from higher point to obstacle 
divided by the difference of elevation), then the two points 
are mutually visib]^. Thus, to determine whether or not 
the bridge near Frenchman's is visible from hill 1065 (point 
346.9 — 749.2, on 3" Map) or is concealed by intermediate 
ground. Take the elevation as 1,065. The distance is 5700 
feet, difference of elevation 266 feet, quotient 21.4. Along 
the line of sight, we find the 960-foot contour on the flank of 
Sentinel Hill to be an obstacle ; distance is 2700 feet, differ- 
ence of elevation 105 feet, quotient 25.7. The 1st (21.4) is 
less than the 2d (25.7) ; therefore the two points are not 
mutually visible. 

37. When a relief map is available of the territory, 
problems in visibility are much simplified. An immense 
number of visibility studies were made by us in France by 
using a little electric bulb on a relief map in a dark room. 
By placing the lighted bulb on any point on the map, the 
whole of the map was marked by shadows or lighted areas. 
The lighted areas correspond- to the visible areas for an ob- 
server at the same point on the ground — the light, in prin- 
ciple, taking the same place of the eye of the observer. The 
lighted and shaded areas were copied on maps and sent out 
for use of the troops, especially the artillery. With well 
made relief maps this method is very accurate. The diffi- 
culty in the use of this method lies in the fact that the pro- 
duction of relief maps is such a complicated process. With 
relief maps the application of the method is unlimited. In 
France by the use of a number of lights we made maps show- 
ing the following: 

(a) The maximum ground behind our lines which could be 
seen from the system of German observation posts. 



20 TOPOGRAPHY 

(b) Maximum amount of ground which could be seen from 
all of our system of posts. 

(c) Same as (a) and (b) above for balloons. (In the case 
of balloons, the little light is suspended above the map at the 
proper point to represent the balloon.) 

(d) In case of advance by us, where to find the best points 
for observation posts. 

(e) Whether or not the objective lines for an attack were 
properly located from a visibility standpoint. 

38. Orientation : — The reading of maps is not wholly 
an indoor occupation. The general, in a comfortable and 
well lighted room, plans his battles from his map ; but the 
regimental officers read their maps in the field, often in the 
rain, and have the problem of correlating the map with the 
ground. The first thing they must do, is # to orient the map ; 
or, in other words, lay the north of the map to the north on 
the ground. By using the compass, find the north, and then 
point the arrow on the map indicating north in that direc- 
tion ; if no north is indicated on the map it is a fairly safe as:- 
sumption that the top is north. If mo compass is available, 
use the North star at night or the sun in the daytime, 
roughly figuring that the sun is in the east at 6:00 AM, 
the southeast at 9 :00 AM, south at noon, the southwest at 
3 :00 PM, and the west at 6 :00 PM. 

39. The following are methods of orientation : 

First method. — Take a map with the magnetic meridian 
marked upon it. Set up a sketching board on its tripod. Put 
the map on the board. Shift it until the magnetic meridian on 
the map becomes parallel to the meridian line of the needle 
. trough. Pin the map down with thumb tacks. Orient the sketch- 
ing board later. 

Second method. — Using a compass, but not the sketching 
board. Lay the map on the ground. Lay the sight line of the 
compass along the magnetic meridian of the map. Rotate map 
and compass together until the needle points north. If sight line 
of compass has been kept along magnetic meridian of map, the 
map is oriented. 

Third method. — No compass or no magnetic meridian; true 
meridian given; .position unknown. Point the hour hand of your 
watch (held face upward) at the sun, if in the northern hemis- 
phere. The line drawn from pivot to the point midway between 
the outer end of the hour hand and XII on the dial will point 
toward the south. Shift your map to correspond. This will give 
a very rough orientation. 

40. Now, having oriented the map, always keep it 
oriented. Do not move the map, but move around the map 
if it is desired to get at it from a new angle. To locate 
yourself accurately on the map select some distant point on 



MAP READING 21 

the ground which you recognize on the map, draw a line 
through the point on the map toward the corresponding 
point on the ground ; repeat this process with other similar 
points. The intersection of the two lines thus drawn on the 
map will be the observer's map position. This method is 
called resection. The method is more accurate as the in- 
tersection approaches a right angle. 

Practical Exercises in Map Reading 

NOTE : — (L) after the number of the exercise indicates that the Leavenworth 
area and the 3" map of the Leavenworth Group are used: (G) similarly indicates 
that the Gettysburg area and the 3" map of the Gettysburg Group are used. 

Practical exercises consist in working out in a section 
room or in the field practical problems which illustrate the 
points in the preceding discussion. Briefly, they consist of 
questions in map reading, drawing in contours and making 
sketches. 

Compass 

1 (L) . At Fort Leavenworth does the compass point 
east or west of true north ? 

2 (L) . What is the magnetic declination at Fort Leav- 
enworth ? 

3 (L). You have received an order to attack in the 
direction, 35°. What will be your compass direction of at- 
tack? 

4. In writing an order, will you give a direction by 
its true or magnetic azimuth? 

5 (L) . You are an observer in the school tower, and 
wish to write to your superior the direction of an object. 
Its magnetic azimuth is 342°. What azimuth do you write 
him? 

6 (L). Having a magnetic needle, how do you orient 
a map by using it? 

7. You have a watch and the sun is shining. How do 
you find north? 

8 (L) . What is the azimuth of the line joining 348.0 
—755.0 and 349.0—756.0? Give it as you would write it 
in an order. 

9 (L) . What is its magnetic azimuth? 

10 (L). You are in command of an organization and 
receive a message from your commanding officer to attack 



22 TOPOGRAPHY 

in the direction 340°. The magnetic declination given on 
your map is 8° 23' E. What compass direction would you 
follow? 

11 (L). You are preparing the orders for a small at- 
tack, and find that the direction of attack is parallel to a 
line joining points 345.0—752.0 and 346.0—753.0. What 
direction will you write in your order as the direction of 
attack ? 

12 (L). You are in command of a battery and one of 
your observers on Sentinel Hill (346.35 — 750.0) reports that 
a body of enemy, estimated at a platoon, are resting along- 
side the main road about 3,000 yards to the north of him 
— magnetic azimuth 359°.- You have the location of the ob- 
server plotted on your map. What will be the true azi- 
muth of the line you will draw from the position of your 
observer in order to locate the enemy? 

13. You are in command of a company and have sent 
a trained officer out to find the azimuth of a certain straight 
road. You receive a message from him that it is 13°. Will 
you assume that he has sent in the true or magnetic azi- 
muth? 

14. You are in command of an American regiment serv- 
ing in a foreign country. You are scheduled to attack and 
the order says in the direction 327°. Upon looking at a map 
it is found that the declination is given on it at 13° W. 
What will be the reading of your compass after you have 
set it to give the direction of attack? 

15 (L). You are holding a section of a battle line along 
ridge running through 355.0 — 747.0. An order comes to you 
to attack in the direction 342°. What do you set your com- 
pass? 

Contours 

1. What is contour interval on the 3" map? 
2 (L). What is the nature of the contour surrounding 
point 344.38—752.35? 

3. Do two contours ever cross? If so, what is repre- 
sented? 

4. The contour interval is 20' on a 3" to a mile map. 
To have the contours spaced the same distance apart on 
any given slope, what should be contour interval on a 2" 
map of the territory? 



MAP READING 23 

5 (L). In which direction does the water flow in the 
stream passing near 343.5 — 748.6? 

6 (L). Which is higher, Sentinel Hill or Bell Point? 

7 (G). What is the name given to the class of contours 
similar to the one running through point 353.75 — 746.25? 

8 (G). In which direction does the water flow in the 
stream running near 355.1 — 743.6? 

9 (G). What is the highest point on the road between 
Gettysburg and Germantown? The lowest? 

Conventional Signs 

1 (L) . What does the conventional sign at each of 
following places represent: 

(a) At 351.8—758.4? 

(b) Vicinity 345.3—755.1? 

(c) At 343.15—756.4? 

(d) At 345.65—751.75? 

(e) At 344.94—755.77? 

2 (L). What does the map show to be the character 
of the country in the vicinity of the following points : 

(a) Vicinity 348.0—757.15? 

(b) Vicinity 351.5—755.0? 

(c) Vicinity 351.3—754.0? 

(d) Vicinity 344.8—754.4? 

(e) Vicinity 347.3—757.5? 

3 (L) . In going southwest to water from house marked 
Tramel at 351.9 — 756.15, what does the map show to be 
the artificial features passed over? 

4 (L) . Are they roads or trails which pass through the 
following points? If roads, are they improved or unim- 
proved ? 

(a) 351.58—754.0? 

(b) 344.0—753.8? 

(c) 350.0—756.15? 

5 (L). What is the character of the ground as shown 
by the contours surrounding point 348.5 — 752.45? Sur- 
rounding point 345.9—752.8 ? 

6 (L). You are on the road at point 350.55 — 751.86, 
leading a patrol of four men, when you are fired on by rifle 
fire from a southwesterly direction. Where would you take 
cover ? 



24 TOPOGRAPHY 

7 (L). You are marching a platoon south along the 
road at 347.7 — 750.45 when you are suddenly shelled from 
the west with high angle fire. Where would you go for 
shelter ? 

8 (L). The ground in the vicinity of point 344.4 — 752.3 
is indicated on the map as meadow land and flat. What 
is the objection, if any, to camping there? 

9 (L). Your aeroplane had stalled and you were forced 
to land at point 349.8 — 754.6. Where is the nearest place 
you might find assistance? 

10 (G). You are ordered to interrupt the York Turn- 
pike running northeast out of Gettysburg. Where would 
be the best place to do it? 

11 (G). Is there underbrush in the woods at 352.89 — 
747.63? 

12 (G). You are on a horse and turn out of column for 
twenty minutes to ride to top of hill 571 (356.85—743.53). 
Can you see anything from the top of the hill ? 

13 (G). What vegetation is shown at the following 
points ? 

(a) At 356.1—750.3? 

(b) At 356.45—742.55? 

(c) At 352.30—748.50? 

(d) At 357.7—745.8? 

(e) At 349.35—745.75? 

14 (G). Is it a cut or fill at 348.2—750.9? At 355.25 
—748.6? 

15 (G). What two types of fences are most prevalent 
on map? 

16 (G). Are there any evergreen trees on the forest 
on Culp's Hill? 

17 (G). What natural feature is shown at 351.58 — 
748.24? 

18 (L). You are with your company in the open at 
347.2 — 747.6 when high angle mortar shells begin dropping 
very close to you. Where do you go? 

19 (L). What is the shortest road distance between 
354.3_744.86 and 354.2—742.8? 

20 (G). You are at crossroads 348.25 — 746.4 in charge 
of a truck train and have orders to proceed to point 350.1 — 
745.5 with the utmost dispatch. It has been raining. Which 
way do you go? Why? 



MAP READING 25 

21 (L). The enemy has been shelling with gas the 
area between Merritt and Pope Hills and Metropolitan 
Avenue. Where will the gas be most dangerous ? 

22 (G). Considering gas alone, is it better to take 
position at 351.5—749.5 or 351.1—748.8? 

Co-ordinates 

1. You are defining a line by co-ordinates. The fol- 
lowing are points on this line, given in order from right to 
left. Write them as they would be written, in an order. 

(1) X = 346.75, Y = 752.62 

(2) X = 345.52, Y = 753.05 

(3) X = 344.18, Y = 754.32 

2 (G). What are the co-ordinates of the top of Round 
Top? 

3 (G). What are the co-ordinates of the church, south 
of the road at Two Taverns (east side of Gettysburg sheet) ? 

4 (G). Designate by co-ordinates the wire fence run- 
ning south from name B. D. Snyder (southeast corner Get- 
tysburg sheet). 

5 (G). What are the co-ordinates of Penn College in 
northwestern Gettysburg ? 

6. How far is it between points 344.0—756.0 and 346.0 
—756.0 ? 

7. How far is it between " 354.9— 748.0 and 355.0— 
749.0? 

8. What is the distance between 354.7 — 745.6 and 356.4 
'_746.7? 

9 (G). What is the shortest road distance, expressed 
in meters, between the crossroads at Two Taverns and point 
354.74—741.62? 

10 (G). Most crossroads on the map are numbered. 
Were these numbers arbitrarily assigned or do they follow 
a system? If a system is followed, what is it? 

Scales 

1. You have counted your strides on a course 5105 feet 
long, extending from A to B. The number of strides counted 
from A to B was 1008 ; on return from B to A you took 
1034 strides. What is the length of your stride in inches? 

2. How many such strides to a thousand yards? 



26 TOPOGRAPHY 

3. On a six-inch to the mile sketch, how many inches 
on the map will be equal to 792 of the strides determined in 
Question 1 above? 

4. The scale of a map is 1 centimeter=l kilometer. 
What is the R.F. of the map ? 

5. What is it expressed in inches to a mile ? 

6. A map is photographed so that the distance between 
any two places on the photograph map is four times the 
same distance on the original map. The R.F. of the original 
was 1:20,000. What is the R.F. of the photograph? 

7. You are in command of a regiment in the enemy's 
country. The map issued to you is to scale 1 :25,000. What 
is the scale expressed in inches to a mile? 

8. What is the best method to represent the scale of 
a map designed for use by people of all races ? 

9. What is the R.F. of a map whose scale is 6" to 1 
mile? 

10. In order to reproduce a map quickly it was photo- 
graphed. You have a copy of this photograph. On the map 
are shown a R.F. and a graphic scale. In using the map 
which will you use? 

11. What is the scale of a map expressed in inches to 
miles when its R.F. is 1:600,000? 

12. You have made a sketch and found that your pace 
scale was incorrect. With incorrect scale map was drawn 
with R.F.=1:10,000. A known distance of 80 yards scales 
100 yards on your map. What is the correct R.F. ? 

Orientation 

1 (L). You are at point 349.0 — 749.2 and have your 
location plotted on the map. Your compass is broken and 
you have no watch. How would you orient your map? 

2 (G). The enemy has just been forced back behind 
Gettysburg from his former lines well to the east. You 
have been given the mission of locating his abandoned 
dumps. You have found one at 352.57 — 749.17. Your com- 
pass is out of order and it is a cloudy day. How will you lo- 
cate the position of the dump on your map ? 

3 (L). You are in the very thick woods along Quarry 
Creek somewhere northwest of the National Cemetery. The 
enemy is about 200 yards north of your position. You want 



MAP READING 27 

artillery assistance. How do you locate yourself so that 
you can report your exact position to the assisting artil- 
lery? 

Visibility 

(Disregard trees, buildings, etc., unless otherwise stated.) 

1 (L). Assume the school tower is 940' above the 
datum of your map. Can an observer in the tower see a 
company at point 348.0—748.65 ? 

2 (L). Can he see a troop of cavalry on the road at 
point 347.2—747.65? 

3 (L). Assume ail trees are 60' high and that if ob- 
serving from a wooded area, the observer can get a good 
view by climbing up 60' in a tree. With the above assump- 
tion can an observer on Sentinel Hill (center of map) see 
infantry at 343.68—753.1? 

4 (L). Assume same conditions as above, can he see 
Plum Hill (346.2—755.9) ? 

5 (L). Disregard trees, etc. Can an observer at 346.0 
— 747.6 see a squadron of cavalry on the road at point 345.5 
—750.38? 

6 (G). Disregarding trees, buildings, etc., can the point 
on road at 350.63—750.0 be seen from top of Wolf Hill? 

7 (G). Can Little Round Top be seen from Wolf Hill? 
Can Round Top be seen? 

8 (G). Disregard trees, etc. Can point 349.0—747.36 
be seen from point 350.1 — 747.5? 

9 (G). Considering all natural features would a com- 
pany of infantry at point 353.2 — 750.8 be visible from hill 
612 (354.0—750.3) to the southeast? 

10 (L). Considering natural features. Your battal- 
ion is at 343.6 — 753.2. Can you be seen from the top of 
Sentinel Hill ? 

Field Exercises in Map Reading 

1 (L) . Place sketch on board with the magnetic meri- 
dian on the sketch parallel to the compass needle when the 
compass reads north. 

2 (L). Orient your map, assuming the compass is 
broken. 



28 TOPOGRAPHY 

3 (L). Assuming the compass reading to the school 
tower is 45°, what is the true azimuth to it? 

4 (L) . What is the true azimuth to the wireless tower? 

5 (L). You are an observer at this point and wish to 
write to your commander the azimuth of a line which by 
your compass is given as 54° 51'. What do you write in 
your message? 

6 (L) . Without looking at the map, what is the differ- 
ence in elevation between this point and Merritt Lake? 

7 (L). Looking at the map, what is it? 

8 (L). Without looking at the map, how far is it to 
the line of barracks north of here? 

9 (L). Look at the map ; how far it is? 

10 (L). Without looking at the map, what do you es- 
timate is the difference in elevation between this point and 
the top of Engineer Hill? 

11 (L): Look at the map; what is the difference in 
elevation ? 

12 (L). What do you estimate the distance between 
the wireless station and the school tower to be? Figuring 
from the map, what do you find it to be? 

13 (L). Looking at the map, is the hill in the vicinity 
of point 347.0—749.3 visible from here? 

14 (L). Without looking at the map, is it visible? 

15 (L). Using map only; could an observer in the 
vicinity of point 346.15 — 747.65 see a patrol at this point? 

16 (L). Check answer by the ground. 

17 (L). Take outline sketch given you and draw in 5' 
contours, looking at the ground and using the elevation 
given on the sketch. 



CHAPTER III 

Use of Instruments 



1. All sketching consists in placing on paper in their 
approximate relative positions the natural and artificial 
features of the terrain. A point B is fully located in rela- 
tion to a point A when its azimuth and horizontal distance 
from A and its vertical distance above or below A are 
known. The fundamental operations of sketching are the 
determination by rapid and approximate methods of the first 
two of the above named co-ordinates, and also of the third 
when the relief of the terrain is to be shown. 

2. There are three general methods of sketching: 

(a)' Compass and notebook method, in which the sketch is 
drawn up later from the notes and partial sketches made in the 
field. 

(b) Compass and drawing board method, in which the sketch 
is made in the field, azimuths being obtained by compass and 
drawn on the sketch by protractor. 

(c) Oriented drawing board or plane table method, in which 
the sketch is drawn directly on the board, which is oriented either 
by compass or backsight. 

3. The Engineer Department issues a standard recon- 
naissance equipment as follows, based solely on the plane 
table method: . 

Equipment 

1 alidade. 1 holder, timing pad. 

1 board, sketching. 1 pace tally. 

1 chest, sketching outfit. 1 pencil pocket. 

1 clinometer, service, with case. 1 tripod, wood, folding. 

1 compass, prismatic. 

Supplies 

12 celluloid sheets. 16 pencils, drawing, H. 

4 erasers, rubber. 4 pencils, green. 

6 pads, timing. 4 pencils, red. 

72 paper sketching board sheets. 3 protectors, pencil point. 

4 pencils, blue. 3 tape, adhesive, rolls. 

This is the equipment used in these schools. 

29 



30 TOPOGRAPHY 

4. The approved distribution is one standard equipment 
to each regimental and battalion headquarters of infantry, 
cavalry, and field artillery, and three to each engineer tool 
wagon giving six per foot company or three per mounted 
company. Headquarters of higher engineer units and divi- 
sion or chief engineers not attached to engineer units re- 
ceive normally three such standard equipments, but divi- 
sion and other engineers may receive a larger number upon 
requisition. 

5. Alidade: — The alidade supplied is a three-sided 
ruler. It is used for three purposes : 

(a) For use as a sighting vane. 

(b) For use as a measuring scale. The three sides are blank, 
and scales of various kinds are pasted on these three sides. The 
scale most in use is the 3" scale of strides. In Chapter I, there 
is shown a set of scales that has been found suitable for the 
three sides of an alidade. 

(c) To determine differences of elevation from the scales 
of slopes provided. It is found most convenient to lay off on the 
scale of the alidade (see the plate of scales shown in Chapter I), 
the differences of elevation corresponding to a difference of 1 
degree of elevation. To find the difference of elevation for any 
distance for more or less than 1 degree, it is sufficiently accurate 
to multiply by the proper number. Plate V shows a scale of 
differences of elevation for 1 degree for distances marked on many 
different scales. 

6. Clinometer : — The clinometer is the instrument for 
obtaining difference of elevation; it measures slopes. 

7. Clinometers are all based on the establishment of 
a horizontal reference line by the spirit level or by the plum 
bob. Trie line of sight is in a vertical plane with the refer- 
ence line and makes an angle with it equal to the slope be- 
tween the eye-piece of the instrument and the point upon 
which the sight is taken. A scale of degrees or grades is 
placed on the instrument so as to measure the slope and is 
usually read in reconnaissance instruments at the same 
time that the line of sight is adjusted on the distant point. 

8. As the slope is usually desired between two points 
on the ground itself it is necessary to sight upon a point 
above the distant point a distance equal to the height of the 
eye above the ground at the time of taking the sight or to 
make proper allowance for the height of the eye above the 
ground in calculating the difference of elevation of the 
two ground points. 



USE OF INSTRUMENTS 



31 




Plate V 



32 TOPOGRAPHY 

9. The clinometer often needs adjustment. It should 
be tested as follows : 

Mark two points, say 50 feet apart. Put clinometer 
sight on one point and read angle of difference to second 
point. Put clinometer sight on second point and read angle 
of elevation to first point. Add the two numerical values, 
regardless of sign, and divide by 2 ; the quotient is the 
true reading. For example, if first reading is 2 degrees 
and second reading 1 degree, the correct reading is H 
degrees. Put clinometer sight line on first point, sight to 
second point, and adjust clinometer until it reads l.V de- 
grees; or if the clinometer does not permit of adjustment 
apply the index error with its proper sign to each reading. 

10. Sketching Board and Tripod form simply a small 
plane table. The tripod has been found to be not only a 
great convenience but is necessary to secure the accuracy 
inherent in the plane table method. 

11. Azimuths are measured in degrees of arc from 
to 360, beginning with zero at the north, and passing 
clockwise, through the east (90 degrees), south (180 de- 
grees), and west (270 degrees), to the north again. 

In work with compass, azimuths are usually referred 
to the magnetic north as zero; they are called magnetic 
azimuths. For accurate maps and surveys, azimuths are 
referred to the true north and may be called "true azi- 
muths," or simply "azimuths." In military operations 
true azimuths are generally used at division and higher 
headquarters (sometimes grid azimuths, when gridded 
maps are used), and magnetic azimuths between division 
headquarters and lower units, and in lower units. The full 
names, viz., magnetic, grid, or true azimuth, should be 
stated ; in military work the azimuths always, unless other- 
wise stated, refer to the true north. 

12. There are other ways of expressing azimuths 
adapted to special conditions or circumstances. In astro- 
nomical work and tables the azimuth is reckoned from the 
south, through W., N., and E., 360° to south again. 

In navigation, azimuths are reckoned from the mari- 
ner's compass, and are called bearings. The dial is divided 
into 32 points and each point into quarter points. 



USE OF INSTRUMENTS 33 

In land surveys bearings are used to indicate direction 
rather than azimuths. They are referred to the cardinal 
points of the quadrant in which they occur usually naming 
the north point or the south point first, thus N 85° W., S. 
70° E. 

13. The Compass is the standard instrument for the 
determination of azimuths in topographical reconnaissance. 
Compasses for sketching and general military use are of 4 
types : 

Prismatic compasses. 
Box compasses. 
Watch compasses. 
Trough compasses. 

Trough compasses indicate the magnetic north but are 
not graduated to show azimuths. Prismatic, box, and watch 
compasses are so graduated that when used as intended 
for the particular type, they will read magnetic azimuths. 

14. Magnetic Declination: — The angle which the 
needle makes with the true north at any place is called the 
declination of the needle or magnetic declination at that 
place (east declination if the needle points east of true 
north ; west declination if the needle points west of true 
north). For latitudes of 60° or less, the declination is ordin- 
arily between limits of 20° east and 20° west, being taken 
now as 9° east at Fort Leavenworth, and 7° west at Gettys- 
burg. 

15. Periodic changes in declination take place, viz. : 
Daily (5' to 15' of arc) ; lunar (less than 1'") ; annual (less 
than 1') ; and secular (a long slow swing covering many 
years). Only the last is large enough to be even noticed 
in military sketching or map reading. In the United States, 
all east declinations are now gradually decreasing, and west 
declinations increasing, at a rate of about 3' per year. Even 
the secular variation is not of importance except for exact 
surveying. 

In addition to the periodic variations, there are irregu- 
lar variations, uncertain in character, due to magnetic 
storms or to local attractions such as iron ore in the hills 
or steel rails on a railway track. 

16. The declination of the compass may be determined 
with sufficient accuracy for military sketching or guiding 
by 3 methods : 



34 



TOPOGRAPHY 



1. Plotting the shadow of the sun at noon; 

2. Observing the magnetic azimuth of the sun or of some 
star at rising and setting; 

3. From Polaris. 

17. The dip of the compass is the tendency of one end 
of the needle to be drawn downward out of the horizontal 
plane because of the location of the magnetic poles beneath 
the earth's surface. The dip is overcome by the use of a 
small adjustable counterweight, placed on the southern end 
of the needle in the northern hemisphere, and on the north- 
ern end in the southern hemisphere. 

18. Distances in sketching may be determined by the 
following methods : 

(a) Pacing on foot. 

The length of a man's pace is about 30 inches. A stride 
is 2 paces. On level ground careful pacing will give dis- 
tances correct to 3 per cent or less. The length of the pace 
decreases on slopes, more rapidly on ascending slopes than 
on descending. The table below shows the necessary cor- 
rection for great accuracy. However, such accuracy is 
rarely required in sketching. 



Slope, degrees 


Ascending 


Equivalent 
Horizontal 


Descending 


6 


90.4 


100 


95.6 


10 


78.7 


100 


91.5 


15 


69.3 


100 


87.4 


20 


58.5 


100 


80.8 


25 


49.1 


100 


68.2 


30 


35.8 


100 


51.4 



NOTE : — Both the shortening 01 the pace and the reduction to the horizontal 
are allowed for this table. 

(b) Pacing mounted. 

The step of the average horse is 33 inches at a walk ; 44 
inches at a trot. 

(c) Timing a horse. 

The speed of the average horse is 1 mile in 16 minutes 
at a walk, 8 minutes at a trot. 

(d) Recording the number of revolutions of a wheel 
by odometer or tallying. 

(e) Speedometer. 

(f) Intersection or resection and location on the map. 
A point may be located by intersection by taking azimuths 
to it from two known points. The unknown point will lie 
at the intersection of the plotted azimuths. An observer 



USE OF INSTRUMENTS 35 

at an unknown point may locate himself by taking azimuths 
to two known points, provided the board be oriented. From 
the known points, plot the corresponding back azimuths 
and they will intersect at the point of observation. 
If it is not possible to orient oneself or to take azi- 
muth readings, an observer at an unknown point may 
still locate the point by resection on three known points, 
as follows : Fasten a piece of transparent paper on the board. 
Mark a point on it anywhere to represent the station and 
draw a ray to each of the three known points. Place 
the transparent paper on the sketch and shift the 
paper until each ray passes through the proper known point 
as already located on the sketch. Prick the point of inter- 
section of the three rays through to the sketch, and the pin- 
hole will give the location of the position occupied. 

(g) Estimating. 

An expert sketcher should be able to estimate dis- 
tances with less than 10 per cent error to about 600 yards, 
and within 15 per cent up to a mile. Objects seem nearer 
than they really are: 

1. When the sun is behind the observer and the object is in 
the bright light. 

2. When seen over a body of water, snow or level plain. 

3. When seen below the observer. 

4. When in high altitudes and very clear atmosphere. 

Objects seem farther away than they really are: 

1. When up a steep hill from the observer. 

2. In poor light such as fog. 

3. When seen across undulating ground. 

Objects are distinguishable to average eyes at the fol- 
lowing distances : 

9 to 12 miles, church spires. 

5 to 7 miles, windmills. 

2 to 2i miles, chimneys. 

2000 yards, trunks of large trees. 

600 yards, individuals of a column. 

500 yards, individual panes of glass in windows. 

400 yards, arms and legs of dismounted men. 

The average distance between street railway and tele- 
phone poles is usually 100 feet. In a large portion of the 
United States the land is divided into sections, and the 
hedges and fences are usually 440 or 880 yards apart. 



36 TOPOGRAPHY 

19. In surveys and large scale mapping, distances are 
obtained by more accurate methods — by steel tape or chain, 
transit and stadia, or triangulation. 

20. Elevations are determined by instruments which 
measure the total difference of elevation by spirit level and 
rod, by barometers which indicate directly the difference 
or by instruments which show the gradient or slope and the 
difference in elevation is then obtained by calculation. 

21. The difference of elevation by spirit level and rod 
is generally obtained only in accurate work. However, the 
clinometer can be set at zero and then used as a level, though 
the results are not very accurate. 

22. Barometers are instruments which show by direct 
reading the results of differences of air pressure. The 
aneroid barometer is graduated so as to show the elevation 
in feet; other barometers require much calculation after 
reading the instrument. Due to atmospheric changes baro- 
metric levelling requires complex adjustment to secure 
even approximate results. 

23. The slope method of determining differences of 
elevation is the one in general use in sketching. 

24. Slopes are usually expressed in degrees (plus for 
rising grades and minus .for descending) ; or in per cent, 
i. e., the rise or fall in feet for each 100 feet horizontal dis- 
tance. They may also be expressed as follows : 

The foot-rise per mile; as "the grade is 50 feet," or "a 50- 
foot grade." 

The number of feet vertical per foot horizontal; 3s 1 on 1, 
6 on 1. 

25. In reconnaissance work, slopes may be determined 
directly by the use of : 

1. The gravity clinometer; 

2. The Abney or spirit-level clinometer; 

3. The locater level (a hand level with object glass grad- 
uated in degrees or per cent) ; 

4. The slope board and plumb line. 

26. For ordinary sketching, the following rough rules 
are sufficiently accurate for determining differences of ele- 
vation on slopes of not more than 10°. 

(a) When slope is given in degrees take product of hori- 
zontal distance .0175, and the number of degrees in the slope; 

(b) When slope is expressed as a grade in per cent take 
product of grade by horizontal distance and divide by 100. 



USE OF INSTRUMENTS 37 

27. Elevations may also be shown by profiles. In pro- 
files, as well as on relief maps, it is usual to adopt a vertical 
scale larger than the one for horizontal distances. The ratio 
of the two scales is called the vertical distortion or exag- 
geration. Ten or 20 feet to the inch is a common scale for 
profiles ; if the horizontal scale is 3" to the mile, the result- 
ing distortions are 176 and 88 times. Both horizontal and 
vertical scales should always be written below profiles. 

28. Contours: — Differences of elevation are shown by 
writing on the sketch numbers corresponding to elevations 
(in feet) , by hachures, or by contours. These have already 
been discussed in a minor way in Chapter II. Contouring 
is hereinafter discussed in so far as is deemed necessary for 
assistance in sketching. 

29. The most difficult part of sketching is the repre- 
sentation of ground forms by continuous contour lines. This 
arises from the fact that contours are on the ground imag- 
inary lines, and their location on the map requires the de- 
termination of all three co-ordinates — azimuth, distance, 
and difference of elevation — of points. 

The shore line of a quiet lake with no outlet, may be 
considered a contour line. As one walks around the lake 
in the direction of the hands of a clock, he always has water 
on his right hand and ground on a higher elevation on his 
left hand. If one desires to follow the above line, he will 
have to turn to the left arid walk up every valley to get 
around the head of the water line, cross the valley line at 
right angle, and then turn to the right, again following down 
the other side of the valley to get around the point of the 
hill or spur which lies between that valley and the next. 
His course will bend back at every little drainage line, cross 
it, and turn again on the other side to get around it. We see 
then that valley contours go in pairs, that is, there is al- 
ways one of the same elevation on each side of the valley. 
They form a sort of V which opens out in the direction of 
water flow; point of the V upstream. Similarly the spur 
contours go in pairs. They form a sort of U which opens 
out to higher ground up the spur. 

The typical contour, then, is a wavy line, alternately 
salient and re-entrant, a series of V's for the valleys and U's 
for the spurs. If then the extreme points of the V's and 



38 TOPOGRAPHY 

U's are determined and these points are connected by a curv- 
ing line, opening out gradually as we go down stream from 
the points of the V, and rounding out to the point of the U, 
we get a line which will roughly represent the contour of 
the ground for the particular elevation. In other words the 
head of the V's or the points where the contour crosses 
the stream, and the points of the U's or the points where 
the contour crosses the line of the watershed between two 
valleys are essential control points for the drawing of any 
contour line ; and having these points well located, the con- 
tour between them can be drawn in by looking at the ground 
in the field. 

It is evident that it will not be practicable to locate the 
points where each contour crosses each stream or ridge 
line. No map can show every change of form of the ground. 
Certain points of the ground are, however, form-controlling. 
Between these form-controlling points, the assumption is 
made that the ground slopes uniformly. The effort there- 
fore should be to locate the form-controlling points, and 
having drawn these in, intervening ones may be spaced 
uniformly. 

30. These form-controlling points are called critical 
points. They are along the valleys and on the watersheds, 
because the bottoms of valleys and tops of ridges are the 
lines where opposite slopes meet, and therefore the con- 
tours themselves change direction most rapidly at their 
crossing of these lines — the ridge lines and the valley lines. 
Indeed at the valley lines and the ridge lines the contours 
begin to turn in an opposite direction. Of course, the forms 
of the ground change at numberless places not in the bot- 
toms of the valleys and on the tops of the ridges, but these 
changes are not very great. 

31. Having placed on the map the critical points, it is 
assumed that the slopes are uniform between these points, 
and points of same elevation as the contour lines are inter- 
polated. After this interpolation, we have on the sketch 
the critical points whose elevations have been determined, 
and a number of intervening points whose elevations have 
been interpolated. Now, if we have the ground in view, 
we may, with a fair degree of truth sketch the contours on 
the map. 



USE OF INSTRUMENTS 39 

32. In sketching, it is always best, if time permits, to 
complete the circuit of an area, make the map close by ad- 
justing the circuit and by a corresponding adjustment of 
the critical points, and then go over the terrain again and 
with the critical points as a guide draw in the contours 
while looking at the terrain itself in order to show on the 
sketch minor changes in terrain which are not obtained by 
the critical points and the interpolated elevations. This 
means simply that the control of the map should be com- 
plete and in satisfactory adjustment before the details are 
added. Should time be lacking it may be necessary to put 
in the details as the control is taken, in such a case an ad- 
justment of the control will require an adjustment of all 
the details. 

34. A little practice with a contoured map will be of 
advanta-ge in obtaining an appreciation of the critical points 
in drawing contours. An area on a map should be selected 
with many changes of directions of stream lines and with 
contours not uniformly distant apart. Then a piece of trans- 
parent paper should be placed over the area, and critical 
points selected and marked with their elevations on the 
transparent paper. The paper should then be removed from 
the map, and effort should be made to reproduce the con- 
tours of the map without looking at it. 

35. The vertical interval between contours of a cone 
system is constant. The distance between contours on a 
map varies with the slope of the ground. The steeper the 
slope of the ground the closer together are the contours on 
the map. The slope of the ground can be obtained from the 
distance apart of the contours on the map to scale and the 
known vertical, interval of the contours. A scale may be 
constructed which, applied to the distance between con- 
tours on the map, will indicate the slope of the ground. The 
tangent of 1° is approximately .0175. If I is the vertical 
interval in feet and R is the representative fraction, then 
the distance apart in inches on the map of contours for a 
one degree s^pe of the ground is 

12 I x R 
.0175 



40 TOPOGRAPHY 

This applied to a map of one inch to one mile with a verti- 
cal interval of 60 feet gives 

12 X 60 

= .65 inch. 



.0175 X 63360 



A scale may be obtained by multiplying the distance for one 
degree by the number of degrees and will be approximately 
correct up to slopes of 10°. Such a scale is called a scale of 
slope equivalents. 

36. Details of Making a Sketch : — Set up the board 
at the point of beginning, station A. Free the needle. Turn 
the board until the needle comes to a rest along, the 
middle line of the needle trough. The board is now oriented. 
Clamp the board by tightening the screw under the center 
of the board. It is unnecessary to clamp very tightly. Place 
a pin at any point of your paper to represent station A. Draw 
a triangle around the pin and write the elevation (generally 
given) of station A. Place the alidade on the board, press- 
ing it against the pin. Select a well defined object or a 
critical point to the right, left, or rear, pivot the alidade 
on the pin, and sight on the object. Draw a ray to the 
point; then measure the difference of elevation. Write 
with light pencil at end of ray the name of object and the 
-degrees of elevation. Plot the distance to the object; then 
determine the difference of elevation by multiplying the 
difference of elevation on the alidade corresponding to 1 
degree for the distance by the number of degrees measured. 
Add this difference (algebraically) to the elevation of sta- 
tion A and write the elevation opposite the point plotted. 
Erase the ray. 

Similarly sight on other objects which can be best 
sketched from station A, and plot them on the sketch. 

Draw in the stream lines, the ridge lines, and the na- 
tural and artificial features of the terrain. If it is not ex- 
pected to make a second trip over the terrain, due to lack 
of time, interpolate elevations on the sketch and now draw 
contours in accordance with the actual form of the ground. 

37. Finally, look ahead, select a suitable point for the 
next station, a point from which much sketching can be 
done, sight on it, draw the ray, measure the degree or per 



USE OF INSTRUMENTS 41 

cent of elevation, set pace tally at zero, loosen clamp screw, 
tighten the needle, pick up the equipment, and start pacing 
to station B, which is best chosen when an extended view 
of the terrain can be obtained therefrom. 

38. On the way to station B, do not be diverted into 
setting up unnecessarily on the road. It is generally possi- 
ble to select a good station from the last station, and it is 
rarely worth the time to set up to sketch some data on the 
way. If deemed necessary, it is sufficient to stop for a min- 
ute, read the pace tally, make a side drawing of the special 
data at the distance as shown by the pace tally, clearly 
identifying it by noting on it the number of paces of the 
pace tally, then proceed on the way, without setting back the 
pace tally. 

39. Arrived at station B, set up as described for sta- 
tion A. Sight back to station A and measure the angle 
of elevation as a check. Calculate from the alidade the 
difference of elevation, add it (algebraically) to the eleva- 
tion of station A, write it down on the sketch at station B, 
and then proceed as before. Sight to points that are to 
appear on the map. Plot them as before. Sight to points 
which were also sighted from station A with a view of ob- 
taining their positions by intersection (being unable to pace 
or estimate them from station A). Plot them at intersec- 
tions, measure and calculate the differences of elevation, 
and write in the proper elevation for each point. Draw the 
terrain, with contours if necessary, sight to distant points 
for later location by intersection from other stations ; finally 
select station C, sight on it, draw ray, measure angle of 
elevation, pick up equipment, and proceed to next station. 

40. Should the route lead the sketcher back to the 
starting point the traverse will close if the work has been 
accurately done. If it, in such case, does not close, the 
amount of failure to do so will indicate the accuracy of the 
work. If the failure to close is so great as to indicate blun- 
der the blunder must be found and corrected. If it is such 
as to be accounted for by the lack of accuracy in the methods 
employed and is so great as to distort the sketch then the 
sketch may be adjusted by the ordinary method, which is: 
draw a line from the final location of the initial point to its 
first location and displace each traverse station, to- 



42 TOPOGRAPHY 

gether with all points located therefrom, in the direction of 
this line and by a proportional part of it determined by the 
ratio of the traversed distance to the station in question 
to the whole traversed distance of the circuit. 

41. Indoor Exercises in Use of Instruments may be 
used with advantage to acquire facility in use. For rainy 
days, and to save time, they are very useful; but they can- 
not take the place of work in the field. 

For indoor work, the student is furnished a chart as 
shown on small scale in Plate VI, and is given such informa- 
tion as he would acquire in the actual operation of sketch- 
ing in the field. He is then required to make the sketch 
with this information, and draw in the contours and other 
features just as he would do in actual field work. 

42. The following problem is an example of indoor work 
in sketching: 

Scale 6 inches to 1 mile. 

10 foot contours. 

Length of stride 72 inches. (Assumed as 72 inches in order 
to use yard scale as stride scale.) 

All clinometer readings to ground line unless otherwise 
stated. Height of eye 5 feet. 

Magnetic declination, 9° East. 

Directions are given by reference to a co-ordinate point to- 
wards which the object is located as seen from the station. By 
the use of the station and the given co-ordinate point the alidade 
may be placed in the direction of the object which is to be located 
as it would be done by sighting in the field. 

Sketch to be drawn on a gridded sheet similar to Plate VI. 

Eequired : 

Sketch west half of area bounded by Somers Road on 
west, Franklin Road on north, Charles Pike on east, and 
Somerville — Sunflower Road on south. Use traverse data 
below ; and make sketch include 200 yards outside traverse 
which 200 yards is given in data. 

A traverse will be run from A, intersection of Somers- 
ville — Sunflower Road (west and east) with Somers Road 
(to north), north along Somers Road to Franklin Road, 
thence east along Franklin Road 1200 yards to high ridge 
in eastern part of area, thence south to Somersville — Sun- 
flower Road, thence west to A. This will give a good road 
on which to pace a base for constructing the map, will com- 
pletely cover the area, and will provide a closed traverse for 
checking the work. 



300 301 

/ndoor Exercise in Jke tching 



764 



76S 



76 Z 



761 



760 



30O 



301 

Plate M 



ion 

764 



763 



76Z 



761 



30£ 



76<T 



44 TOPOGRAPHY 

Set Up at A 

A is located on the sheet at co-ordinated point 300.68 — 
760.90. Known elevation at A is 167 feet. Road runs in a 
westerly direction toward Somersville, straight as far as 
visible, about 500 yards, direction towards co-ordinate point 
300.00 — 761.05. Same road runs in an easterly direction, 
straight as far as can be seen, about one-half a mile, direc- 
tion towards point 302.00 — 760.60. Somers Road runs 
northward direction towards point 300.75—762.00, to Bend 
B, estimated about one-half -a mile distant. 

Farmhouse of John Somers is in northeast corner of 
road intersection. 

Land east of Somers Road (as far as visible, about one- 
half mile) , and north of Somersville — Sunflower Road (about 
500 yards), is plowed. 

South from A is a knob (Al), direction towards point 
300.65 — 760.00, distance estimated 900 yards, slope read- 
ing plus | degree. 

A spur extends northwesterly from this knob to point 
A2, direction towards point 300.17 — 760.00, distance from 
A estimated 500 yards, slope reading plus f degree. 

West of A is a head A3 of a dry stream running north- 
eastwards. The point A3 in is direction of co-ordinate point 
300.00 — 760.97, distance estimated 35 1 yards, slope reading 
zero. This same dry stream crosses the Somers Road at 
A8, distance estimated 400 yards north of A, slope reading 
minus J degree. 

Northwest of A is a knob A4 (running north and south) 
direction towards point 300.00 — 762.20, distance esti- 
mated 700 yards, slope reading plus J degree. 

Northeast of A is a flat knob A5, direction towards 
point 302.00 — 761.90, distance estimated 1 mile, slope read- 
ing plus £ degree. 

A6, the saddle between A5 and A2 is in the direction of 
A5 from A, distance from A estimated 125 yards, slope 
reading minus one degree. 

At a point A7, 450 yards eastward of A, the Somersville 
Road crosses a dry stream running towards the northeast, 
slope reading minus J degree. 



USE OF INSTRUMENTS 45 

Sketch in the topography including the contours so far 
as may be done from the above data. 

The next station will be in the direction of B. A sight 
towards it has already been taken above. 

This ends set up at A. 

Traverse Towards B 

Stop at A8 but do not set up. 

The distance of A8 from A is found to be 205 strides. 
This checks very closely the estimated distance given above. 
The dry stream from A3 to A8 is noted to be practically 
straight, and just beyond A8 this stream bends towards the 
north passing about one hundred yards east of B. 

Continue Traverse Towards B 

Stop at A9, northern edge of plowed field, but do not 
set up. 

Distance from A to A9 is 250 strides. Northern edge 
of plowed field as far as visible about \ mile extends in the 
direction towards point 302.00—761.13. 

Continue Traverse Toivards B 
Total distance- A to B is found to be 375 strides. 

Set Up at B ' 

Backsight towards A, slope just a little above zero 
(about 3 feet). 

Correct location and elevation of B to conform to the 
correct distance given above. 

The road ahead runs towards co-ordinate point 300.40 
— 763.00 as far as point C (intersection with Franklin Road) 
about | mile from B (plot direction carefully as probably 
next station will be towards C), slope reading to C is zero. 
On east side of road at B is farmhouse with mail box 
marked "Henry Somers." 

From B, hill A4 is found to be in the direction of point 
300.00—761.37. The intersection of this line with the direc- 
tion line from A checks fairly closely the estimated dis- 
tance of A4 from A given above. 

The top of hill A5 cannot be seen very clearly from B, 
A5 appears to be in the direction of point 302.00 — 761.75, 



46 TOPOGRAPHY 

and the slope reading about plus | degree. The intersection 
of this line with the direction given from A indicates that 
the estimated distance of A5 from A was too great by about 
400 yards. Correct location and elevation of A5. 

To the northwest, in the direction of point 300.00 — 
762.35, is a lone tree Bl, estimated distance 400 yards from 
B, which marks end of the flat spur extending northwards 
from hill A4 ; slope reading zero. To the northeast is a 
round knob B2, direction towards point 302.00 — 762.60, es- 
timated distance 1000 yards, slope reading plus \ degree. 

A saddle connecting B2 with A5 cannot be clearly seen 
from B. 

To the northeast, towards point 301.90 — 763.00, is point 
B3 the lower end of a wide spur running down from B2, 
distance estimated 500 yards, slope reading zero. 

To the north towards point 301.40 — 763.00, distance 
estimated 300 yards, the dry stream A3-A8 bends to the 
west of north. 

Northeast of B, towards point 302.00—762.10, is B4, 
the foot of a draw leading towards the saddle between B2 
and A5, distance estimated 400 yards, slope reading minus 
I degree. 

Sketch in so much of the topography including contours 
as can be done from the above data. 

The next station will be in the direction of C (a sight 
towards it has already been taken). 

This ends set up at B. 

Traverse Towards C 

Stop and set up at B5, on Somers Road 300 strides 
north of B. 

Short Set Up at B5 

Slope reading B5-B is zero. 

To northeastward, towards point 302.00 — 762.70, is 
B5a, the southwest corner of woods W (large trees, no un- 
derbrush) , distance estimated 200 yards. The western edge 
of woods W runs a little east of north. The southern edge 
of woods W extends past B5b, which is towards point 302.00 
— 762.35, distance estimated 500 yards, slope reading zero. 

A draw extends from just south of B5a through B5b. 



USE OF INSTRUMENTS 47 

The dry stream from A3-A8 passes just east of B5a 
and continues on to the west of north. 

From B5 the direction of B3 is towards point 302.00 — 
761.60. The intersection of this line with the direction 
given above from B checks fairly closely the estimated dis- 
tance of B3 from B. 

From B5, the direction of Bl is towards point 300.00 — 
761.20. The intersection of this line with the direction given 
from B, checks closely the estimated distance of Bl from 
B. 

About 200 yards ahead, at point B6, the road crosses a 
dry stream running from the southwest towards the north- 
east, slope reading B5-B6 minus f degree. 

End of set up at B5. 

Continue Traverse Towards C 
Stop and set up at B6, 365 strides from B. 

Short Set Up at B6 

The dry stream through B6 comes from the direction 
of point 300.00 — 761.90, and continues to the northeast to- 
wards point 300.85 — 763.00. About 100 yards northeast of 
B6 it is joined by the stream from A3-A8-B5a. 

End of set up at B6. 

Continue Traverse to C 
Distance from B to C is 645 strides. 

Set Up at C 

Backsight to B, slope minus Vg of 1 degree. 

Correct location of C to conform to correct distance. 

The Somers Road ends at C where it runs into the 
Franklin Road which runs eastwards towards point 302.00 
— 762.66, as far as D, estimated more than 1000 yards dis- 
tant, slope reading zero. To the west, the Franklin Road 
runs in prolongation of the above towards Westport. 

To the northwest, towards point 300.00 — 763.13, is 
point CI, head of a dry ravine running towards the north- 
east; distance of CI from C estimated 250 yards, slope read- 
ing minus 1| degrees. 



48 TOPOGRAPHY 

About 400 yards southwest of C, towards point 300.00 
— 762.50, is C2, slope reading C-C2 is plus I degree. The 
crest of a spur runs from C2 through C to the northeast 
towards C3. The direction of C3 is towards point 302.00 — 
764.00, distance from C estimated 700 yards. Slope reading 
C-C3 is minus f degree. 

Hills A5 and B2 are concealed from C by woods W. 

Sketch in so much of topography including contours 
as may be done from the above data. 

Sketch now looks like figure T 13 in back of Topography, 
except it is twice as large as that given in the figure. 

The next station will be in the direction of D (sight to 
D already taken). 

This ends set up at C. 

Traverse Towards D 

Stop and set up at C4 where the dry stream from B6 
crosses the Franklin Road 180 strides east of C. 

Short Set Up at CU 

Slope reading C4-C is plus \ degree. 

C4a, northwest corner of woods W, is towards point 
301.35—762.00, distance estimated 150 yards. The north- 
ern edge of the woods parallels the Franklin Road. The dry 
ravine through C4 runs practically straight from B6 and 
continues to the northeast towards point 301.60 — 764.00. 

End of set up at C4. 

Continue Traverse Toivards D 
Distance from C to D is 585 strides. 

Set Up at D 

Backsight to C, slope reading minus Ye of 1 degree. 

Correct the location and elevation of D. From D the 
Franklin Road continues eastward towards point 302.00 — 
762.70, straight for about a mile. 

From D, knob B2 (previously sighted from B) is to- 
wards point 301.75 — 762.00, slope reading plus 1 degree. 
The intersection of this line with the direction plotted from 
B shows that the estimated distance of B2 from B was 



USE OF INSTRUMENTS 49 

about 175 yards short. Correct the location and elevation 
of B2. 

From D, C3 is towards point 300.25—764.00. The in- 
tersection of this line with direction of C3 from C shows 
that the estimated distance of C3 from C was a little too 
great. 

Slope reading to Dl, a point about 300 yards to the 
east on Franklin Road where the road begins to run down 
hill is minus | degree. 

D2, on the downward slope to the north, is towards 
point 301.90 — 764.00, distance estimated 300 yards, slope 
reading minus 1 degree. 

The eastern edge of woods W is on the line towards 
point 301.20—762.00. The northeastern corner, D3, is esti- 
mated to be about 150 yards from D. 

The next station will be in the direction of E which is 
towards point 301.54 — 762.00, distance estimated 250 yards, 
slope reading plus § degree. 

Sketch in so much of topography including contours 
as may be done from the above data. 

This ends set up at D. 

Traverse Towards E 

Distance D-E is 125 strides. This checks the estimated 
distance above. 

Set Up at E 

Backsight to D, slope reading is minus 1| degree. 

The point E is on a small spur extending westwards 
into woods W from north end of knob B2. 

To the southwest of E is El, the southeast corner of 
woods W, direction towards point 300.60 — 762.00, distance 
estimated 200 yards. 

The next station will be located in the direction of F 
which is on spur between B2 and B3, direction from E is 
towards point 301.54 — 762.00, distance estimated 250 yards, 
slope reading zero. 

Sketch in so much of topography including contours 
as may be done from the above data. The sketch should now 
look like figure T14 in the back of pamphlet on Topography, 
except it is twice as large as that given in the figure. 

This ends set up at E. 



50 TOPOGRAPHY 

Traverse Toicards F 

Distance E-F is 130 strides. This checks the estimated 
distance to F. 

Set Up at F 

Backsight towards E, slope reading minus f degree. 

From F, former station B is towards point 300.00 — 
761.10. This line passes through station B as plotted on 
the map. This indicates that no errors have been made in 
running and plotting traverse from B to E (Note: Station 
A cannot be seen from F). 

From F, B2 is in the direction of point 302.00—762.78 
and B3 is in the direction of point 300.00 — 761.55. This 
checks the former location of those points. 

From F, hill A5 is in the direction of point 302.00 — 
761.20, slope reading zero. Intersection of this line with 
the direction of A5 from A now definitely locates A5. The 
rough intersection formerly made from station B is found 
to be very close. 

The draw from B4 starts at Fl ; direction of Fl from F 
is towards point 301.47 — 761.00, distance estimated 400 
yards, slope reading minus 1 degree. To the southeast of 
F is F2 which is the head of a dry ravine running towards 
the northeast; direction of F2 from F is towards point 
302.00—761.50, distance estimated 350 yards. F2 is about 
the same height as Fl. 

East of F is F3, another point in the dry ravine from 
F2, direction from F is towards point 302.00 — 762.10, dis- 
tance estimated 475 yards, slope reading minus 1 degree. 

The next station will be in the direction of G which is 
on spur between A5 and A, direction of G from F is towards 
point 301.47 — 761.00, distance estimated 600 yards, slope 
reading minus i degree. 

Sketch in so much of topography including contours 
as may be done from the above data. 

This ends set up at F. 

Traverse Towards G 
Distance F-G is 330 strides. 



USE OF INSTRUMENTS 31 

Set Up at G 

Backsight to F, slope reading zero. 

Correct the location of G. 

From G, station A is in the direction of point 300.00 — 
760.30, and station B is in the direction of point 300.00 — 
761.68. These lines pass through those stations respec- 
tively. This indicates that the running and plotting of the 
traverse is correct. 

From G, A5 is towards point 302.00—761.90. This 
checks the former location of A5. 

South of G is Gl, northeast corner of plowed ground 
mentioned under A above, direction from G is towards point 
301.47—761.00, distance estimated 330 yards. From Gl 
the northern edge of the plowed ground runs toward A9, 
and the eastern edge runs due south. 

South of G is G2, point in dry ravine from A7, direc- 
tion toward point 301.57 — 761.00, distance estimated 500 
yards, slope reading minus l ! i-, degree. 

Southeast of G is G3, another point in same dry ravine 
as G2, direction towards point 302.00 — 761.10, distance es- 
timated 550 yards, slope minus 1% degree. 

The next station will be at H which is south of G on 
the Somerville — Sunflower road, direction from G is to- 
ward point 301.41 — 760.00 (the intersection of this line 
with the road locates H), slope reading minus i degree. 

Sketch in such topography including contours as may 
be done from the above data. 

This ends set up at G. 

Traverse Toivards H 

Stop at Gl and G2. 

Gl is found to be 165 strides. 

G2 is found to be 250 strides from G. These check 
the former estimated distances to Gl and G2. The direc- 
tion of A7 and G3 are noted to be very close to that already 
plotted. 

Continue Traverse Towards H 

Distance G-H is found to be 430 strides. This checks 
very closely the above location of H by intersection. 



52 TOPOGRAPHY 

Set Up at H 

As far as can be seen, about 800 yards, the road to 
Somerville continues directly in prolongation of the section 
already located. 

On road to east of H a dry ravine crosses the road at 
HI, distance estimated 300 yards, slope reading minus -\ 
degree. This dry ravine comes from a little west of south 
through HI and continues on and appears to join the G2- 
G3 ravine about 200 yards east of G3. 

Southeast of H is H2, end of spur running down from 
Al, direction of H2 from H is toward point 301.60—760.00, 
distance estimated 200 yards, slope reading is zero. 

From H, hill Al is in the direction of point 300.65 — 
760.00, and spur A2 is in the direction of point 300.00 — 
760.30. The intersection of these lines with the directions 
formerly given from A checks very closely the estimated 
distances from A. 

Sketch in as much of topography including contours 
as may be done from the above data. Sketch should now 
look like Figure T15 in the back of Topography, except that 
it is twice as large as the sketch in that figure. 

This ends set up at H. 

Traverse Towards A 

Distance H-A is 400 strides. This checks very closely 
the location already plotted. This indicates that no ap- 
preciable error has been made in running and plotting the 
traverse. 

End of Data 

Place title and name on sketch. 

Practical Exercises in Use of Instruments 

1. From station A, you take a clinometer reading to 
the ground line at B. The height of your eye is five and 
one-half feet above the ground at A. The clinometer read- 
ing is two degrees down. The distance to B is paced off 
and found to be 200 strides (60 inches each). Is B higher 
or lower than A, and how much ? 



USE OF INSTRUMENTS 53 

2. A hill a half-mile away has a clinometer reading, 
from station A, of plus six degrees. The elevation of sta- 
tion A is 1480 feet. What is the elevation of the hill? 

3. The distance to a wireless tower, as plotted by you 
on your sketch, is 550 yards. The clinometer reading to 
the mound at the base of the tower is | degree descending. 
The reading to the top of the tower is 3i degrees ascending. 
What is the height of the tower? 

4. A man climbs a tower at A and reads the slope to a 
crqssroad B. The clinometer reads minus 4^ degrees. He 
descends 70 feet to the ground and reads again to the same 
point. The reading is now minus ^ degree. About how 
many yards away is the crossroad? 

5. Your elevation at A is 770 feet. Clinometer reading 
to ground at crossroad E is plus 2 degrees, distance 1000 
yards, and from A to base of flagstaff at F is plus 3 degrees, 
distance 1500 yards. (Height of eye, 60 inches.) What is 
elevation of crossroad E? Of base of flagstaff F? 

6. Marks have been put on two posts, A and B. Sight- 
ing from A to B, your clinometer reads minus £ degree. 
From B to A, the reading is minus H degrees. What is the 
correct reading from A to B ? 

7. Does the instrument read too high, or too low, and 
how much? 

8. How will you correct in the future for this error in 
your instrument — 

(a) On plus readings? 

(b) On minus readings? 

9. Location of a Point by Intersection: — (Use 
blank grid sheet.) Locate on a sheet of paper the point A 
at 301.0 — 763.0. Your sketching board is set up at A and 
oriented. (True north at top of paper.) Scale of sketch 
to be 6" to the mile. You sight ahead to a new station B, 
which is on the line from A to co-ordinate 305.0 — 764.0. 
Draw in this line of sight. You sight on a hill on your right 
with a flagstaff (F) on line from A to co-ordinates 305.0 — 
760.0. Draw in this line of sight. (The distance to F is 
estimated as 600 yards, but it is probable you can get 
another sight later from the new station B.) You then pace 
off the distance from A to the new station B, and find it to 



54 TOPOGRAPHY 

be 360 strides (72 inches each). You set up your board, 
plot your new location B, and then sight on flagstaff F, which 
lies in the direction B to co-ordinate 304.0 — 760.0. Locate 
the flagstaff F on the sketch. What is its general direction 
from B? How many yards from A to F? From B to F? 

10. Location of a Point by Resection on Two Known 
Points: — (Use blank grid sheet.) 

Captain E, who is making a six-inch-to-the-mile sketch, 
finds himself at an unknown point, C, which he needs to 
locate. He has on his sketch the locations of two prominent 
points, A and B, both visible from C. A is at 301.0 — 761.1; 
B is at 303.3 — 762.0. Orienting his board at C, Captain 
E sights at and draws in lines of sight towards A and B. 
On his sheet the line CA has an azimuth of 195°; the line 
CB has an azimuth of 120°. How many yards is C from B? 

11. Location by resection on three points: (Use blank 
grid sheet and tracting paper.) 

On his sketch (6" equal 1 mile) Captain E has three 
prominent points. A at 300.5—764.2, B at 302.0—764.2, C 
at 304.1 — 763.7. All are visible from his present unknown 
location X. Setting up his sketching board (unoriented, as 
his compass is broken), Captain E puts a sheet of tracing 
paper on the board over his sketch, puts in a pin near the 
middle and calls this point (X) . (Put tracing paper over 
grid sheet and plot X near center of sheet.) He draws 
rays to A, B, and C. Ray XA has an azimuth of 297° ; ray 
XB, of 355° ; ray XC, of 45°. 

1. Locate X on the sketch. 

2. How many yards from X to A ? From X to B ? From 
X to C? What is the general direction from A to X? 

3. The elevation of B to 592. The slope reading X— B 
is 3 degrees down. The slope reading X — A is 1 degree up, 
X — C, 1 degree down. Disregarding height of eye, what are 
elevations of points X, A and C ? 

12. Place a sheet of tracing paper over area of 3" 
Leavenworth sheet bounded by Millwood Road, Kickapoo 
Road, Atchison Pike, Co-ordinate 343.0. Select 21 critical 
points and write their elevations in proper place ; put noth- 
ing else on tracing paper. Set aside map. Draw in 20-foot 
contours. Place on map and compare result. 



USE OF INSTRUMENTS 55 

13. Drawing of road sketch in room from data given 
(use blank grid sheet) . Scale 6" to 1 mile. Vertical inter- 
val, 10 feet. This problem, uses compass for practice. 

NOTE No. 1 : — Unless otherwise stated, all ground in this prob- 
lem is meadow land. 

NOTE No. 2: — All slope readings are taken at the height of the 
eye; that is, all lines of sig'ht are taken on a point (in the air) which 
is above the object a distance equal to the height of the observer's eye. 

NOTE No. 3:— Strides are 60 inches. 

NOTE No. 4: — All roads are unimproved earth roads. Special 
data such as size of rails on railways, character of houses for defense, • 
etc., are omitted (for brevity in description). 

Set Up at A 

A is a point on road with co-ordinates 301.2 — 760.3 on 
the gridded sheet. Known elevation of A is 875 feet. 

Al, road with magnetic azimuth 78 degrees, distance to 
top of ridge estimated 600 yards, difference of elevation 
estimated plus 7 feet. 

A2, same road as above (fenced in and discontinued on 
western side of road) with magnetic azimuth 258 degrees, 
distance to ridge top estimated 350 yards, slope plus 4 de- 
grees ; two wooden houses at top of ridge. 

A3, road with magnetic azimuth 170 degrees, distance 
100 yards, difference of elevation estimated minus 10 feet. 

A4, along edge of ridge, magnetic azimuth 275 degrees, 
distance estimated 200 yards to edge of woods, 400 yards 
to top of ridge, slope plus 6 degrees. 

A6, smoke stack, magnetic azimuth 66 degrees, location 
to be obtained by intersection later. 

Sketch in, by looking at terrain: 

(a) Ravine from station, magnetic azimuth 258 degrees, 200 
yards long, 10 feet deep. 

(b) Ravine from station, magnetic azimuth 263 degrees, 150 
yards long, 8 feet deep. 

(c) Corn on right; meadow at left; wire fences. 

Sight station B, magnetic azimuth 350 degrees. 
End of set up at A. 

Traverse Toward B 

Stop at A7, bottom of stream line, 125 strides, estimated 
5 feet below A. Stream line comes from magnetic azimuth 
290 degrees (made up of two stream lines joining 200 yards 



56 TOPOGRAPHY 

away with magnetic azimuths of 320 degrees and 240 de- 
grees), turns at this point (where it crosses the road) and 
continues with magnetic azimuth 67 degrees, distance 400 
yards, estimated difference of elevation 15 feet. Woods, 
magnetic azimuth 270 degrees, distance 400 yards, differ- 
ence of elevation estimated 50 feet ; ridge top estimated 600 
yards, slope plus 4^ degrees ; meadow land to left, corn to 
right. 

Continue Traverse Toivards B 

Meadow land to left, corn to right; A to B, 240 strides. 

Set Up at B 

Backsight to station A, slope, minus f degree. 

Bl, woods, magnetic azimuth 270 degrees, distance 30 
yards, slope plus 15 degrees. 

B2, along low ridge line to stream line junction, mag- 
netic azimuth 90 degrees, estimated distance 550 yards, 
slope minus 2| degrees ; stream line through A7 joins stream 
line with magnetic azimuth 310 degrees, new stream con- 
tinues with magnetic azimuth 110 degrees. 

A6, smoke stack, 82 degrees magnetic azimuth ; slope 
to its estimated foot, minus one-fifth degree. 

Sketch in, by looking at terrain : 

(a) Large brick wall inclosure around smoke stack, estimated 
square with sides 300 yards long, walls 70 feet high, buildings 
in center and along south wall. 

(b) Road from this inclosure, magnetic azimuth 270 degrees, 
to road junction with road from magnetic azimuth 120 degrees, 
distance estimated 350 yards; road then continues with mag- 
netic azimuth 340 degrees. 

(c) Railway 20 yards beyond main road and parallel to it, 
crossing road from brick inclosure. 

Sight station C, magnetic azimuth 10 degrees. 
End of set up at B. 

Traverse Toward C 

Stop at B3, bottom of stream line, 210 strides, estimated 
20 feet below B. Stream line runs magnetic azimuth 90 de- 
grees for 200 yards, then runs to stream junction at B2. 
To left of road at B3, stream line enters woods, magnetic 
azimuth 260 degrees, distance estimated 200 yards, dif- 
ference of elevation estimated plus 50 feet. Ridge top es- 



USE OF INSTRUMENTS 57 

timated 500 yards, slope plus 5 degrees. Meadow land to 
right. 

Continue Traverse Toward C 

Stop at B4, B to B4, 300 strides ; woods to edge of road 
on left, top of ridge invisible, slope plus 10 degrees. 

Continue Traverse Toward C 

Woods at edge of road to left; corn to right; B to C 
452 strides. 

Set Up at C 

Back sight to B, slope, minus 1 degree. 

CI, railway, magnetic azimuth 20 degrees, 55 strides, 
difference of elevation estimated minus 10 feet. 

C2, center of railway cut 10 feet deep, 100 yards long, 
magnetic azimuth 90 degrees, 45 strides, top of cut es- 
timated minus 7 feet. 

C3, direction of road, magnetic azimuth 165 degrees. 

C4, woods at edge of road, magnetic azimuth 270 de- 
grees, top of ridge invisible, slope plus 10 degrees. 

C5, railway from point 1200 yards with magnetic azi- 
muth 97 degrees, to a point 500 yards with magnetic azi- 
muth 110 degrees, then curves in general direction of mag- 
netic azimuth 320 degrees. 

C6, old earth road, magnetic azimuth 20 degrees, crosses 
one railroad at 55 strides, second railroad (continuation of 
curve) at 150 strides. 

C7, woods at head of stream line, magnetic azimuth 
90 degrees, estimated distance 300 yards, estimated dif- 
ference of elevation minus 60 feet. 

Sight station D, magnetic azimuth 330 degrees. 

End of set up at C. 

Traverse Toward D 

Woods on both sides, slope down on right, up on left, 
C to D, 215 strides, actually about 210 strides as road bends 
slightly to right of straight line C — D. 

Set Up at D 

Draw in road C — D, bending somewhat to right of 
straight line C — D. 



58 TOPOGRAPHY 

Backsight to C, slope minus 3£ degrees. 

Dl, woods to right, magnetic azimuth 40 degrees, slope 
minus 6 degrees for at least 200 yards. 

D2, woods to left, magnetic azimuth 220 degrees, slope 
plus 8 degrees for at least 100 yards. 

Sight station E, magnetic azimuth 335 degrees. 

End of set up at D. 

Traverse Toward E 

Woods on both sides until beginning of cut, then 
meadow land. Slope down on right, up on left until be- 
ginning of cut. At stride 140, wood road comes from mag- 
netic azimuth 100 degrees, crosses road DE, and continues 
with magnetic azimuth 300 degrees. D to E, 260 strides, 
actually about 250 strides, as road bends about half way to, 
say 20 yards to left of straight line D — E. 

Set Up at E 

Backsight to D, slope, minus 3 degrees. 

Draw in road D— E, bending to left of straight line 
D — E about 20 yards at stride 125. 

E is located in center of cut at top of ridge; cut 100 
strides long, 20 feet high at center; rocky ledges. 

El, direction of ridge, magnetic azimuth 30 degrees, 
slope plus 1 degree for 500 yards. 

E2, direction of nose, magnetic azimuth 260 degrees, 
slope zero for 150 yards. 

E3, direction of ridge, magnetic azimuth 167 degrees, 
slope zero for 700 yards. 

E4, stream line, magnetic azimuth 300 degrees, slope 
minus 6 degrees. 

E5, wooded hill top, magnetic azimuth 333 degrees, 
location to be obtained by intersection later, slope zero. 
Sight station F, magnetic azimuth 335 degrees. 
End of set up at E. 

Traverse Toward F 

Woods and slope down on left; meadow and slope up 
on right, E to F 260 strides. 



USE OF INSTRUMENTS 59 

Set Up at F ' 

Backsight to E, slope, plus 5 degrees. 

Fl, railway 15 yards from F on side toward E, mag- 
netic azimuth on left 210 degrees for at least 600 yards; 
magnetic azimuth on right 42 degrees for 300 yards where 
road bends to right around nose of hill. 

F2, railway 20 yards beyond F, magnetic azimuth on 
left 213 degrees for about 500 yards where it bends to right ; 
magnetic azimuth on right 46 degrees for 300 yards where 
it bends to right around nose of hill. 

Sight station G, magnetic azimuth 277 degrees. 

Traverse Toward G 

One hundred strides, road to right, magnetic azimuth 
55 degrees, road junction at this point estimated 30 feet 
below F. 125 strides, stone house 50 feet to right and wood 
house 30 feet to left, estimated 30 feet below F, point being 
on road and at foot of slope to top of hill to north ; 175 strides 
stone school house 100 feet to right 30 feet up hill side, 
wood house 20 feet to left, cultivated land to left, cultivated 
land to right except on steep wooded hill side. 

335 strides to G. 

Set Uv at G 

Backsight to F, slope, plus 2 degrees. 

G2, hill sighted from E, has a long flat top, 55 degrees 
magnetic azimuth to southern end. 

G3, 10 degrees magnetic azimuth to northern end. 

G4, 55 degrees, 200 yards, estimated difference of eleva- 
tion plus 40 feet, point where slope changes, thereafter be- 
ing more rapid rise to top of hill. Corn to south and 
southwest, orchard and brush on other side of road. 

Sight station H, magnetic azimuth 317 degrees. 

Traverse Toward H 

175 strides, road coming in on left from magnetic azi- 
muth 245 degrees, trees on both sides of this road, brick 
house at end, distance 200 yards, estimated difference of 
elevation minus 5 feet below G. 



60 TOPOGRAPHY 

175 strides, 2 wood houses on right of road, on edge of 
road. Corn on left, brush and meadow on right. 
350 strides to H. 

Set Up at H 

Backsight to G, slope plus § degree. 

Stream line from 176 degrees magnetic azimuth crosses 
road at H, going 355 degrees to large creek 375 yards. 

HI, farm road to wood house, 68 degrees magnetic 
azimuth, 250 yards to wood house, estimated plus 50 feet 
difference of elevation. 

H2, north edge of flat hill, 60 degrees magnetic azimuth, 
distance found by intersection of line G — G3 with H — H2. 

H3, small knoll on left, 270 degrees, 100 yards, differ- 
ence of elevation plus 37 feet. 

H4, wooden house 400 yards farther along road which 
has a general direction of 317 degrees magnetic azimuth, 
and crosses large creek at 375 yards, estimated difference 
of elevation where road crosses creek minus 15 feet. 



CHAPTER IV 

Applied Military Sketching 



1. Military sketching aims at showing the features of 
the terrain that are of special importance to the operation 
that the sketch is intended to serve, — camp, march, or en- 
gagement. The features that are usually important in all 
sketches, whether these features are natural or artificial, 
are: those which affect the movement of troops and trans- 
port both on and off the established lines of travel; those 
which affect the observation of both friendly and enemy 
troops from the ground and from the air; and those which 
affect the fire of the various arms. 

2. The ability to produce a satisfactory sketch signifies 
not only the necessary topographical skill, but also a know- 
ledge of military operations in general as well as informa- 
tion as to the immediate operation that is to be undertaken 
on the terrain to be mapped or sketched. Even with the 
most exact knowledge of the information that the sketch 
should show, limitations as to time and as to how much 
detail a sketch of the scale adopted can show restrict the 
amount and the kind of data that will be placed upon the 
sketch. Those features which, in the judgment of the 
sketcher, have a material bearing on the operations to be 
undertaken are the features to show. 

3. Military Sketches or Reconnaissances May be 
Classified as follows : 

Road sketch, 

Reconnaissance of a railroad, 

Reconnaissance of a stream or river, 

Reconnaissance of woods or forest, 

Reconnaissance for a camp or cantonment, 

Reconnaissance for a position (position sketch), 

Outpost sketch, 

Place sketch, 

Panoramic or landscape sketch. 

61 



62 TOPOGRAPHY 

Sketches may also be classified as mounted sketches 
or foot sketches, and as combined sketches or individual 
sketches, depending on the methods by which they are 
made. 

4. A Complete Road Sketch should show data on the 
following subjects: 

The road: Gradients, especially the steepest; net 
width of roadway; if paved, width, kind and condition of 
paving; width and depth of side ditches, and whether wet 
or dry ; if not paved, character of soil, sand, clay or gravel ; 
kind of fences and width between them ; telegraph and tele- 
phone lines. The sketch should also show where the road 
is in embankment or in cutting; where wagons cannot 
double or pass, and where foot troops cannot march along 
the side between the wagon track and the fences. 

Bridges: Material of piers and abutments; type and 
material of superstructure, as girder, truss, arch, suspen- 
sion, wood, steel, stone, etc. ; width of roadway, and clear 
headroom; safe load. Of bridges over the road, clear width 
and height; for bridges over streams, the nearest bridges, 
above and below, and whatever information can be obtained 
about them. 

The country : Character of cultivation or natural vege- 
tation ; areas and density of adjacent timber ; marshes and 
fords, kinds of fences, nature of soil; general configuration 
of surface, especially high hills, long ridges or valleys, bluffs 
or slopes too steep to scale, and practicable routes to their 
crests. 

Streams crossed: Name, width, depth, character of 
bottom, fordability, and surface velocity in swiftest current 
(velocity in miles per hour or noted as sluggish, moderate, 
quick, or swift) ; elevation of high-water marks in relation 
to the road ; which bank is the higher at crossing and above 
and below, and how much; accessibility of water for stock; 
fords at or near crossing, length, depth and steepness of 
approaches; levees or embankments, height and thickness 
on top ; if navigable, to what distance above and below and 
for what class of vessels — steamers, flatboats, rowboats. 

Town and villages passed through: Name, location on 
map, and population ; names of streets to be traversed ; ma- 



APPLIED MILITARY SKETCHING 63 

terial, as stone, brick, frame, log ; location of railway depots, 
post, telegraph, and telephone offices ; of drinking fountains 
and watering troughs; of elevators, storehouses or other 
accumulations of food or forage ; of blacksmith, wagon, and 
machine shops. 

When ordered to make a complete examination of a 
town or a village, note beside the foregoing, location and 
size of principal buildings, halls, court and school houses, 
churches, banks, jails, and their ownership ; sources, maxi- 
mum quantity, quantity and distribution of water supply; 
sanitary conditions and disposal of wastes ; location of rail- 
roads, depots, freight houses, sidings, etc. ; condition and 
width of roads entering from surrounding country, and 
names of places to which they lead ; location and extent of 
open spaces, and of large buildings standing apart; loca- 
tion and extent of high ground within range, especially 
that from which streets can be enfiladed. 

Railroads crossed : Name, gage, single or double 
track; sidings and loading platforms at point of crossing; 
crossing (at grade, over, or under) ; distance and name of 
nearest station each way. 

Telegraph and telephone lilies:' Location of central 
offices, of batteries ; where the lines lead ; condition, number 
of wires. 

5. A Complete Reconnaissance of a Railroad should 
furnish the following data : 

The line : Local name, terminal points and distances 
between stations and other points; gage; single or double 
track ; condition of roadbed, ties, and rails ; drainage and 
liability to overflow or washouts ; facilities for repair ; con- 
dition of right of way for marching troops along the line. 

Tunnels and bridges : Number and location ; dimen- 
sions ; strength of bridges ; means of destroying and repair- 
ing; of blocking traffic. 

Rolling stock : Number and nature of engines and 
cars available ; capacity for transporting troops between 
given points; facilities for constructing armored trains, as 
spare rails, steel plates, old boilers, etc. ; location and capa- 
city of shops and store yards. 



64 TOPOGRAPHY 

Stations : Name and location ; facilities for entrain- 
ing and detraining troops with wagons and horses; plat- 
forms on through line and sidings ; ramps ; sidetracks, num- 
ber and capacity ; turntables ; water tanks ; fuel supply ; stor- 
age facilities ; derricks or cranes, crossovers for teams and 
pedestrians. Facilities at hand for hospitals, camps, de- 
pots ; for feeding men, heating coffee, watering horses dur- 
ing temporary halts. 

Other communication*: Telegraph lines; number and 
location of stations, number of wires; connections; parallel 
highways, roads, rivers, or canals; means of access from 
same to railroad; junctions and crossings of other lines; 
relative elevation ; facilities for laying temporary switches 
and sidings at stations or between crossing lines. 

Defensibility: Heights commanding line of road; de- 
fense of stations ; defense of road and telegraph lines against 
raiding parties ; structures exposed to demolition ; defense 
and attack of same; defiles and river crossings. 

6. Reconnaissance of a Stream or River: — The 
banks are designated as right or left' if on the right or left 
hand as facing down stream. Data required for complete 
reconnaissance. 

The valley: General configuration, heights of limit- 
ing ranges, and positions of passes or roads crossing them ; 
commanding ground from which a stretch 'of the channel of 
considerable length can be enfiladed by artillery; forest 
growth on or near banks ; soil and cultivation of the valley ; 
roads parallel to river, and means of access to them from 
the river. 

The stream: Its width, depth, and velocity; naviga- 
bility, as for steamboats, flatboats, rowboats, rafts, and 
head of navigation for each ; nature of obstructions to navi- 
gation and possibility of removing or avoiding them ; season 
of high and low water ; average rise and fall ; rapidity of 
rise and fall, and causes; amount of drift; character of 
banks and relative command. Quality of water; amount 
and kind of sediment borne; usual period and thickness of 
ice. 

Tributaries and canals: Width, depth, navigability, 
and means of crossing. Nature and purposes of canals; 



APPLIED MILITARY SKETCHING 65 

dimensions and lifts of locks ; time for lockages ; means of 
destroying locks and effect of destruction ; floating plant 
found. 

Bridges and fords : As in road report. Also, for 
bridges, note position of the channel and navigable width 
between piers; height of arches and lower chords above the 
water at different stages ; dimensions and operation of draw 
spans. Note the exact position of fords and the marks on 
both banks by which they may be found ; length, width, and 
nature of bottom ; velocity of current ; position of deep holes ; 
aids to crossing. Note nature of approaches to bridges and 
fords ; width of roadway, slopes, soil, effect of weather and 
traffic. Note especially the defensibility of bridges and 
fords. 

Ferries, boats and other means of crossing: Position 
of ferries; approaches and practicability for horses and 
loaded wagons ; sizes, number, and kinds of boats ; method 
of propulsion, sites for military bridges or ferries ; char- 
acter of site for construction, use and defense ; proximity of 
islands and tributary streams ; approaches and slope of 
banks ; width of river and maximum surface velocity of 
current; materials for the construction or repair of boats, 
bridges, or ferries. 

Inundations : Places suitable for inundations by dam- 
ming or obstructing a narrow bridge span, or by cutting a 
levee or dike. Note raised roads on ground liable to natural 
or artificial inundations and the safest route to follow by 
known landmarks when the road is overflowed. An exten- 
sive inundation 2 feet deep on level ground is a serious ob- 
stacle unless the roads are very sound and marked by trees, 
posts, etc. Even when so marked, a dip in the roadbed of 
3 or 4 feet may render the road impassable. A railroad bed 
is soon washed out even by a slight overflow. 

7. Reconnaissance of Woods or Forest: — Note all 
roads and paths, and all hills, ravines, and streams within 
the wood or striking the edges ; kinds of trees, density and 
growth; underbrush, prevalence of vines, marshy or large 
open spaces; practicability of forming new roads by cut- 
ting ; creation of obstacles by felling trees ; if there are no 
roads, traverse the shortest practicable path between the 



66 TOPOGRAPHY 

point of entrance and point of exit, and mark bowlders or 
blaze trees, set stakes, or otherwise indicate this path, and 
also give compass bearings of the route to be followed. Note 
the exterior forms of the woods, whether parts of the edge 
flank other parts; connection with the neighboring pieces 
of wood by scattered trees or clearings ; undulations of the 
ground that would give cover to attacking force or to de- 
fenders. 

8. A Reconnaissance for a Camp or Cantonment : — 
Site : Location, elevation, and area ; sanitary features, 

such as drainage, dryness, and general character of top soil ; 
proximity of swamp ground or stagnant ponds. 

Communications: Sufficiency of existing roads and 
paths, maximum grades, probable condition under heavy 
traffic and in bad weather, location and kind of materials 
available for improvement or repair, railroad or water com- 
munication and terminal facilities of same. 

Water and fuel: Location, kind and quantity of fuel 
at hand; quality and quantity of water; facilities for filling 
water carts, for watering animals and for washing and bath- 
ing; nature of supply, as wells, springs, running streams, 
and its reliability. 

Shelter and conveniences : Proximity of trees, brush, 
wood, hay, and straw for huts and bedding ; of markets ; of 
towns and villages. 

Defensibility : Location of outposts and guards ; loca- 
tion and character of defensive positions in or near the 
camp ; force required to hold positions which may command 
the camp. 

9. An Outpost Sketch is a sketch made from the 
friendly outpost. It is principally a sketch of the enemy's 
position, and may simply cover ground in front of an outpost 
line or it may serve to extend a road or position sketch 
toward the enemy farther than the farthest point which 
can be reached by the sketcher. The outpost sketch may 
also include certain parts of the friendly outpost, in which 
case it does not differ in that terrain from a position sketch. 

Since it is impossible to proceed beyond certain points 
in the outpost, all terrain beyond these points, in fact the 
greater part of the outpost sketch, must be ascertained by 



APPLIED MILITARY SKETCHING 67 

intersection. For this purpose, it is necessary to sketch 
from at least two points in the outpost. 

An outpost sketch must show as much of the enemy's 
terrain and dispositions as is practicable or desirable. Special 
consideration must be given to the following points : 

Landmarks, especially such as can be used by the artillery 
for adjustment and by the infantry for ranges. 

Woods, ravines, houses, etc., which may be used to conceal 
the enemy. 

Roads, trails, etc., which may be used by the enemy for com- 
munication. 

Telegraph and telephone lines. 

All hostile works which may be of use to patrols or in 
planning and executing an attack should be located as ac- 
curately as means will permit. This should include the fol- 
lowing : 

Hostile machine guns. 

Hostile outguards. 

Enemy batteries, being specially careful to state whether 
positions are known or unknown. 

Enemy lines, position, length, direction, etc. 

Enemy observation posts, balloons, etc. 

Enemy movements, written or marked on the sketch as may 
be necessary. 

General character of the terrain, such as contours, etc. 

Character of our own terrain, as much as may be desired. 

10. Position Sketch : — A reconnaissance for a position 
usually includes the selection of the position or a recommen- 
dation as to a proper selection (see also text-books on fortifi- 
cation) . The object of the sketch must be kept in mind and 
the features that most influence the considerations which 
call for the map must be shown or indicated. 

The principal object of such a reconnaissance is to ob- 
tain the data for putting the troops on the most favorable 
positions that the ground affords. An officer with troops who 
is furnished the sketch should be able to go on the ground 
and follow the lines as shown ; therefore such details of the 
terrain as will be readily recognizable must be shown on 
the map, in addition to the military features. The military 
features shown by the sketch should include the following : 

Natural and artificial features of the position, particularly 
those related to cover, shelter, command, dead spaces, and ob- 
stacles. 

The field of fire, including ranges to or location of impor- 
tant targets. 



68 TOPOGRAPHY 

Depth of the position. 

If desired, most suitable locations for lines of defense, etc. 
Nature of flanks. 
Communications. 

Positions in front of the line which are suitable for outposts. 
Artillery positions. 

Possible positions from which the enemy can secure advan- 
tages of command, enfilade, and ground observation. 

11. A Place Sketch is a sketch of an area, made by 
a sketcher from one point of observation. The directions 
and data for elevations may be measured as in any other 
sketch, but the distances (and consequently the elevations) 
are obtained by estimation or by comparison with known 
distances. For some reason, the sketcher is limited to one 
point, as would be the case in an observation tower on a por- 
tion of the outpost of which the tower was the only point 
from which a sketch could be made. 

A place sketch will show such information as is specially 
needed for the mission. If for an outpost, it will show the 
data required for an outpost sketch ; if for a position, it will 
show the data required for a position sketch, etc. 

12. A Panoramic Sketch is a pictorial representation 
of a certain portion of the terrain, as seen from a given 
point, drawn on the principle of perspective; the more 
important features of the landscape being so emphasized 
that they may be identified with certainty. It differs from 
a map in that objects are portrayed as if viewed from a 
definite point on the earth's surface, instead of from an 
infinite distance above it; furthermore the features of the 
ground are, as far as possible, shown as they appear, in- 
stead of by means of standard conventional signs. 

13. Object of Panoramic Sketch: — A panoramic 
sketch is used in war : 

(1) To provide firing data for artillery and machine guns. 

(2) To furnish graphical information of enemy front line 
activities. 

(3) To assist observers at fixed observation posts in deter- 
mining the map locations of enemy activities. 

It will be seen from the foregoing that the panoramic 
sketch serves, essentially, as a means of identifying and lo- 
cating targets for the indirect fire (immediate or eventual) 
of artillery and machine guns. Therefore the information 
it shows should be so exact that battery and machine gun 



APPLIED MILITARY SKETCHING 69 

company commanders may rely upon it for the computation 
of firing data. 

14. The Mil: — As the information furnished by a 
panoramic sketch is largely employed in indirect fire., it 
is desirable that the angular unit used in panoramic sketch- 
ing should be identical with the one used in fire control. 
This unit is the mil. However, if ruler with mils is not 
available, the direction may be given in degrees as deter- 
mined by a compass. 

In all panoramic sketching, a battery commander's 
ruler (called B.C. ruler) or a musketry rule will be found 
of great assistance. 

15. Time Element: — The panoramic sketch may be 
made in a few minutes by a scout during a reconnaissance ; 
or it may be made by an observer from a permanent ob- 
servation post, in which case an abundance of time will be 
available. Whoever makes the sketch must bear in mind 
that the sketch is to be used by another person, either by 
the higher commander in his study of the sector, by the 
battery or machine gun company commander in his conduct 
of fire, or by future observers at the same post ; hence, cer- 
tain accepted fundamentals as to identification, informa- 
tion and technique must be observed. 

The type of sketch that is to be made will depend upon 
the time element. Occasionally time is the all-important 
element, as when the sketch must be quickly ready to as- 
sist a battery or machine gun company commander in the 
rapid preparation of fire; hence rapid methods of calibra- 
tion of the paper with regard to the landscape will be em- 
ployed. When positions are stabilized, the sketcher will 
use instruments in making measurements of all horizontal 
and vertical angles and will, accurately, place the points so 
located on the paper, according to some adopted horizontal 
.and vertical scale. Such a sketch will- be almost photo- 
graphic in its exactness. 

16. Panoramas and Perspective Sketches: — A 
sketch made deliberately with exact instruments and cover- 
ing all of the terrain visible from a given observation post 
is often called a panorama. The sketch made by the scout 
during the reconnaissance of a position sometimes is known 



70 TOPOGRAPHY 

as a perspective sketch. There is really little distinction 
between them, one sketch grading into the other according 
to the time employed on it. Blank sheets should be fur- 
nished the sketcher for either type of sketch. These sheets 
should contain a series of parallel vertical lines and a 
series of parallel horizontal lines. By adopting "a certain 
scale for the space between the vertical lines; e.g., 100 
mils, it will be possible to make a series of sketches all to 
one scale, which, when pasted together end to end, will 
give the sketcher a complete panorama. On the other 
hand the lines on the paper lend themselves to the more 
hurried methods of calibration as will be explained later. 

17. There are two essentials of a panoramic sketch 
which must stand out with particular prominence; first, 
clearness of identification; second, information furnished. 
Accuracy is another essential. 

Identification'. — The sketcher must remember that If 
the person using his sketch cannot identify the terrain 
represented, then his work is valueless. Hence the sketcher 
must neglect nothing that will add to the certainty of 
identification. Of course the sky line is likely to be the 
greatest aid to identification of the sector and hence should 
not be omitted, although the objects thereon may be far out 
of artillery range. Objects in the mid-distance and fore- 
ground also should be included when they will aid in this 
step although they may have no particular military value. 
Lastly the data to be entered at the bottom of the page, 
showing the place where the sketch was made and indicat- 
ing the orientation, are essential to the identification of 
the sector. 

Information-. — The object of the sketch is to convey 
information. Hence, although the sketch may be a work 
of art; and although the one who picks it up may have no 
difficulty in identifying the sector; yet if that sketch does t 
not show the features of the terrain that are of importance 
in the military situation existing, it is valueless. That the 
information furnished should be accurate is self-evident; 
otherwise the sketch loses much of its value. 

Drawing : — While drawing is not so important as some 
other things in sketching, the sketcher must remember cer- 



APPLIED MILITARY SKETCHING 71 

tain fundamentals. First, the sketch must not be obscured 
by unimportant details. That is, the important features 
must be emphasized at the expense of the unimportant. 
Hence it is just as important to know what to leave out as 
it is what to put in. Whatever is done, the sketcher must 
not attempt to show the sector by a mass of shading such 
as might be employed for artistic effect in a picture. Such 
a procedure will hide essential details rather than empha- 
size them. The fewer lines that can be used to convey the 
desired information, the better the work. 

However the drawing need not prove troublesome. 
Any man who can handle a pencil well enough to make an 
area sketch can make a satisfactory panoramic sketch, re- 
gardless of whether or not he has any of the instincts of an 
artist. More often than not he will make a more valuable 
sketch than the trained artist because he will not be tempted 
to make a pretty picture and so hide military information. 

18. Technical Devices : — Since the sketch must enable 
the user to identify the sector quickly, it should convey to 
the eye a rough picture of the terrain as it actually is seen. 
To secure this picture a few technical devices should be 
employed. 

System of 'parallel lines: — First of these technical de- 
vices is the principle of perspective. This is a means of 
making use of the fact that distance to the eye is indicated 
by the angle which an object of given height subtends at the 
eye. The greater the distance the smaller the angle and 
hence the smaller the object appears to the eye. Thus a 
row of objects of a given height extending into the distance 
apparently will grow smaller as the distance becomes greater 
until they finally vanish into a point on the horizon. In 
order to get the same effect of distance or depth in a sketch, 
the following principles of perspective should be applied. 

Parallel lines, if prolonged appear to come together or 
vanish at a point called the vanishing point. Perhaps the 
commonest example of vanishing of parallel lines is to be 
found in the track of a level railroad. 

Parallel lines not horizontal, vanish in a point above 
or below the horizon. 

Parallel lines also parallel to the plane of the picture 
are drawn parallel in the sketch. 



72 TOPOGRAPHY 

19. Consecutive ci'est lines : — The effect of distance 
can be given in a mechanical way by varying the weight of 
line. Since objects seen close at hand are large and clear 
and decrease in size and clearness as they recede from the 
observer, this principle must be applied to sketching. The 
nearest features must be the largest and the heaviest of 
line, while they should become smaller and lighter of line 
until the most distant crest line is reached, which must be 
the faintest of all. 

20. Broken lines : — By refraining from actually join- 
ing intersecting crest lines, a further technical means is 
employed of giving the effect of depth to the sketch. This 
gives the effect of haze found on distant slopes. 

21. Ground Slopes and Forms: — One of the funda- 
mental requirements of a good sketch being clearness, it 
is essential that all useless details be omitted. On the other 
hand the general slopes and configurations of the ground are 
of military importance and the question arises as to how 
to show this ground form without detracting from the 
clearness of the sketch. This is effected by using the nat- 
ural and artificial features that exist on the ground, drawn 
to conform to the principles of perspective. 

The position and shape of a road may indicate a rise 
over a crest in the foreground, a gentle slope to a turn, and 
finally a gradual rise to a crest, where it disappears. A 
telegraph line would bring out the same facts. (See Plate 
VII.) These features are of military importance and there- 
fore must be shown, but, by means of these features the 
configuration of the ground also is indicated without intro- 
ducing useless lines or detracting from the clearness of the 
drawing. In the same way the form of the hills may be 
brought out by a few lines flowing in the direction of slope. 
In the case of the wooded hill (Plate VII) the lines are short 
and irregular, representing the tops of trees, while in the 
bare hill the lines are smoother. 

The tendency of the average sketcher, upon completion 
of his sketch, is to attempt to add to the general artistic 
effect by introducing shading of various descriptions. This 
should not be done, for the only result accomplished is to 
detract seriously from the clearness of the work. It should 



APPLIED MILITARY SKETCHING 



73 



be borne in mind that the panoramic sketch is not a land- 
scape drawing, but is a skeleton chart, devoid of everything 
of no military value, in which clearness is one of the prime 
essentials sought. Therefore, unless the sketcher is thor- 
oughly familiar with shading and its use, it should be elim- 
inated. 

22. Conventional Signs: — Since simplicity and clear- 
ness is the key-note of a good sketch, the simplest possible 




f.j*. i 






^»~s.. 



BAR.E 






Plate VII 

symbols to represent natural and artificial features should 
be used. For this reason conventional symbols or signs 
are employed that are easily and quickly made, and which, 
by slight variations, represent and identify features found 
in any given locality. For the purpose of rapid identifica- 
tion of features depicted, it is necessary to make the con- 
ventional signs look as much like the features they repre- 
sent as possible. 

Possibly the features most commonly met in a landscape 
are tree groups. They should be represented by an ir- 



1 \ TOPOGRAPHY 

regular line for the tops and a more or less straight line 
for the near edge. Care should be taken to make the ir- 
regular line ve«ry irregular to prevent its confusion with the 
lines of the sketch such as hills, crests, lines, etc. (Plate 
VIII, Fig. 1.) 

23. Control: — The inexperienced sketcher examining 
a landscape is confused by the many details that meet his 
eye. Important and unimportant features are so numer- 
ous and mixed together that it seems a hopeless task to 
pick out and recognize the simple framework on which 
the whole is built. It is necessary, therefore, that the eye 
be trained to separate a landscape into its main mass groups, 
disregarding details, and bounding these masses by a single 
line so that the relative position and size of the masses, 
both vertically and horizontally, shall form the framework 
of the whole. The lines bounding hills, mountains, crests, 
and tree groups, and their intersections with each other, 
form such mass groups; and once having recognized these 
main bondary lines, and having plotted them in their rela- 
tive horizontal and vertical relation, the sketcher has a 
framework that is complete, after which important details 
may be inserted quickly in their correct positions. A sim- 
ple method of recognizing these mass groups is to half close 
the eyes and examine the country, when these groups will 
become immediately apparent. 

24. Detailed Operatic us of Making the Sketch: — 
Equipment: The following equipment is used: 

1. Compass. 

2. Field glasses. 

3. B. C. ruler or a musketry rule. 

4. Penknife. 

5. 1 medium hard (2H) and 1 medium soft (2B) pencil. 

Colored pencils may be used. 

6. Eraser. 

7. A map of the terrain to be sketched, from which the 

names of villages, destination of roads and railway 
lines, names of rivers, streams and mountains may be 
obtained, and ranges to prominent features measured 
by scaling. 

8. Sketching pad of smooth paper. This paper preferably 

should be ruled in faint lines in some convenient manner 
as a guide and aid to the sketcher. 

Locations of the sector : — The first step necessary is to 
determine, by actual inspection, the limits of the sector. 
If the sector has been plotted on a map previously it is neces- 



APPLIED MILITARY SKETCHING 



75 



sary for the sketcher to orient himself and determine the 
sector limits accurately from the map. Having located the 
limits of the sector, the sketcher measures it with a B.C. 
ruler, musketry rule or some other instrument for meas- 
uring horizontal angles. Since the panoramic sketch is 



Treai i Underbr uih 




Re 



e Po" 



fe ' i<J 



lie 



.!**= 



K r 



Target 












Ronqs(yds) 


5000 


4J500 


2 150 6000 .^000 


3 mi 


3000 


Def (mils) 


c 


HO 


i.00 ISO 2B0 


340 


,5lO 




5 ketch made 
from point 
(343.0-747.0)- Map 
Weother:clear 



Fig. 2 



/ 



Panoramic Sketch 

o/ front of 

1-jt Division 

Drawn under the direction of Ma f Oen A 

5 oopm tOJepf,/°i9 

by Mej X 



Plate VIII 



drawn to a definite horizontal scale it is necessary to deter- 
mine this scale before proceeding. The artillery sketching 
pad is divided into eight vertical zones between the two 
limiting vertical lines. Hence if the sector measures 800 
mils, the distance between any two adjacent vertical lines. 



76 TOPOGRAPHY 

will represent 100 mils; if the sector is 400 mils, the dis- 
tance between adjacent vertical lines will represent 50 mils, 
etc. For a pad ruled in any similar convenient manner 
the scale of the sketch may be determined. 

It is essential that data giving location of sector and 
sketching point be recorded immediately, for the impor- 
tant reason that unless this information is shown, the sketch 
is of slight value to anyone else attempting to use it. Casual- 
ties among sketchers and observers are frequent and it 
should be mandatory on all sketchers to complete these 
data, as soon as the sector to be sketched has been deter- 
mined. The sketch thus becomes valuable at once to others 
as soon as any military information appears on it, and in- 
creases in value in proportion to the completeness and ac- 
curacy of this information. 

Orientation of the sketch : — Just as a map must, in 
order to make it of any value, have indicated upon it the 
points of the compass, so must a panoramic sketch have 
some indication of direction. In the latter case this indi- 
cation is only an approximation and serves more for identi- 
fication of the country than a correct designation of direc- 
tion. At the bottom of the sketch an arrow indicating the 
magnetic north should be drawn. Its direction is deter- 
mined in the following manner : 

Turn the sketching pad into a horizontal position. Sight 
along any vertical line at or near the center until this line, 
if prolonged will pass through the exact point on the land- 
scape through which it passes in the sketch. The sketch is 
now oriented. 

Holding the pad in this position place a compass on it at 
the bottom of the sketch and allow the needle to come to rest. 

Through the position of the compass draw an arrow par- 
allel to the compass needle. Note the place from which the 
sketch is made, the name of the sketcher, date, weather, as 
regards visibility and the hour of the day. 

This last point is important as the visibility changes 
from day to day and from hour to hour, hence unless indi- 
cated, an officer who was using a sketch of a particular sec- 
tor might imagine that he was in the wrong area unless he 
knew that the condition of visibility had changed. If time 



APPLIED MILITARY SKETCHING 77 

permits, a sketcher may choose the hour of the day when the 
visibility is best for the area before him. Thus early morn- 
ing is best for a sector to the east while shadows of late after- 
noon will serve to bring out successive ridges in an area to 
the west. 

Examination of the sector: — Before proceeding fur- 
ther, examine the sector with and without glasses. The 
ground should be studied in an effort to get a clear mental 
picture of the formation and to separate it into its fundamen- 
tal mass groups ; the foreground mass of defilading screen, 
successive crests, the background or horizon. Glasses often 
will disclose crests, hollows, etc., capable of hiding targets 
which otherwise might be overlooked. A little study will 
separate the important from the unimportant details and 
the sketcher then is ready to proceed along definitely 
thought out lines, to conform to the object of the sketch. 

Selection of reference 'point and horizontal control: 
— In order to make the horizontal scale of practical value, 
an origin of horizontal measurement must be selected from 
the terrain and must be plotted and indicated on the sketch. 
A sketch without a clearly indicated reference point is an- 
alogous to a map without means of orientation. The ref- 
erence point may or may not be in the sector included by 
the sketch. It should preferably be in the sector, but 
owing to the fact that the reference point must be a dis- 
tinct, easily identified point, it is possible that a given sec- 
tor may be devoid of any point that could fulfill these condi- 
tions. In this case such a point should be selected as close 
to either limit of the sector as possible and an arrow, labeled 
reference point, drawn immediately above the sketch point- 
ing in the direction of this reference point. The point 
selected should further be described briefly as, "Reference 
point, lone pine tree on sky line," etc." Under normal con- 
ditions a suitable point can be chosen in the sector and 
indicated directly on the sketch. Since it is the origin of 
horizontal measurements, its angular designation will be 
zero, a fact which further identifies it. 

In the selection of a reference point, the following con- 
siderations should govern: 



78 TOPOGRAPHY 

(a) It should be easily seen and identified even under un- 
favorable conditions of visibility, hence, not too far away (as 
a distant mountain-peak on the sky line) . 

(b) It should be of such a character that it cannot be 
entirely destroyed by artillery fire. 

The most suitable reference points during the late war 
were found in the middle distance, preferably, features of 
the terrain, such as a small hill of distinctive shape, a well 
denned crossroads or road fork, the point where a road 
crossed a crest, or the intersection of a stream with a road 
or railroad, etc. These were found to satisfy all condi- 
tions better than houses, towers, chimneys, trees or dis- 
tant mountains. 

By means of the plotted reference point and the ver- 
tical guide lines, a basis of horizontal control is established. 
By actually measuring with the mil ruler the horizontal 
deflection of important points from the reference point, 
these points may be plotted horizontally on the sketch in 
their true rciuiion. This reference point preferably should 
be placed on one of the vertical lines of the sheet. 

Vertical control : — Vertical control, while not so im- 
portant as the horizontal must be considered by the sketcher 
if he would avoid distortion. Unless some line of vertical 
control is adopted a sketcher often will enlarge the vertical 
scale of one side of his sketch, due to the amount of detail 
which appears there, while the other side, being without 
military features, may be compressed. Usually it is cus- 
tomary for the sketcher who is not using instruments to 
choose a vertical control line to which he will refer all other 
elevation, the reference being wholly by eye. 

In choosing the vertical control line for the sheet, it 
should be placed so as to leave the greater part of the area 
of the sheet for the showing of most important targets. To 
properly portray the details of the ordinary terrain a cer- 
tain amount of exaggeration of the vertical relations is de- 
sirable, otherwise successive crest and tree lines will be so 
crowded as to make the picture obscure. Ordinarily the 
sketcher who has adopted a vertical control line need not 
concern himself with the need of exaggeration, since he will, 
unconsciously, exaggerate in the course of his drawing. 



APPLIED MILITARY SKETCHING 79 

If, however, the sketch is to be a true panorama 
in which the site of each target is desired, the vertical re- 
lations of the several points to be noted may be obtained 
and the points plotted on the sheet in their proper relation 
according to an adopted vertical scale. Some schools ad- 
vocate a vertical exaggeration of two to one. This amount 
is excessive and the sketcher should be cautioned against 
too great an exaggeration, lest he make his sketch gro- 
tesque and add to the difficulty of identification. 

Framework: — The deliberate method consists simply 
of plotting a few important or critical points by means of 
the horizontal and vertical control. With these points es- 
tablished, the framework can then be drawn in through 
them by reference to the terrain. Typical critical points 
are crests of hills, intersections of crests, houses, limiting 
points of roads, limits of tree groups, etc. Through these 
plotted points draw the outline of the terrain. 

In the hasty method the pad is held vertically in front of 
the eye. By looking over the top of the pad at the landscape, 
and at the same time moving the pad to or from the 
eye, a point will be reached at which the two limiting ver- 
tical lines of the pad will intersect, if prolonged, the cor- 
responding limits of the sector. Holding the pad here the 
sketcher draws in lightly, at the extreme top of the sheet, 
the sky line and as many other important points as possible, 
comparing the outline directly with the country as he 
glances over the top of the pad. This procedure automa- 
tically locates the framework horizontally. When com- 
pleted, the pad is lowered into a comfortable horizontal 
position and the framework so drawn is carried down into 
its proper position on the sheet, especial attention being 
given to locating the framework correctly by means of the 
vertical control. 

This method is much more rapid than the other and 
after a little practice equally accurate results can be ob- 
tained with it. It has the advantage of eliminating con- 
stant identification of plotted points with corresponding 
ground points, and the consequent loss of time. 

The framework by either method should be done 
lightly with a hard pencil. If time permits it can be gone 



80 TOPOGRAPHY 

over later and corrected where necessary. More atten- 
tion can then be paid to characteristic shapes and forma- 
tion, and to relative vertical relations. The principles 
of perspective also should be applied. 

By using a sheet of transparent celluloid, the same 
size as the sketching pad blank, ruled in the same manner 
as the blank and attached at right angles to the pad, the 
sketcher may calibrate his sketch, simply by looking through 
the celluloid, and noting on which line or in which space 
each feature falls. It is a simple matter, then to sketch 
those features in the same areas on the paper. 

Filling in : — With the framework established it is a 
comparatively simple operation to fill in with those details, 
the importance of which is governed by the purpose of the 
sketch. Time being a factor, and the object being prin- 
cipally to locate targets, the framework is sufficient and 
no unneccessary time should be spent on filling in, and the 
framework itself should be only a rough approximation. 
Time and the object sought govern the amount of detail 
shown, and it is here that the knowledge of what to omit 
makes itself manifest. 

Speed and simplicity are gained in locating details by 
plotting limiting points on the framework and then draw- 
ing in the details between these points. Points where 
roads, telegraph lines, fences, etc., appear and disappear 
over crests, horizontal limits of tree groups and settle- 
ments, are features that can be located this way. Simple 
points may be located by referring them to points on the 
sky line under which they are vertically situated. 

With the soft pencil the sketcher should go over the 
drawing and vary the weight of lines in it, bearing in mind 
that the weight of line and size of objects decrease uni- 
formly as they recede from the observer, the lightest lines 
being the objects seen furthest away. Usually the immedi- 
ate foreground is unimportant and little time should be de- 
voted to it. . 

Designation of targets and important points : — When 
a target is plotted on the sketch its deflection from the ref- 
erence point and range from the sketcher's position as well 
as the target designation, should be entered in an appro- 



APPLIED MILITARY SKETCHING 81 

priate place on the sheet. Vertical lines are drawn from 
the top of the sheet and terminate in an arrowhead in 
the exact point on the sketch where the point in question 
is located on the ground. Directly at the top of the line 
the description of the point so located is written diagonally, 
so that it can be read with the sketch held in a normal 
position. Conventional signs for targets should not be used. 
They serve only to add unnecessary detail to the sketch and 
destroy clearness. Since the right of the target as viewed 
by the observers is the point on which firing data are com- 
puted, the vertical line should indicate the location of the 
right of the target, and if further identification is necessary, 
its width in mils may be indicated. This woud mean then, 
that the arrowhead locates the right of the target, and that 
the target extends to the left of this point so many mils. 
Simplicity in designation of targets can be accomplished 
by using definitely understood abbreviations; e.g., "I" for 
infantry deployed, "A" for artillery in position, etc. The 
reference point always should be indicated as such and 
may further be given its corect name if known. For quick 
identification the line to this point may be made heavy or 
doubled. According to the judgment of the sketcher and the 
purpose of the sketch, any information may be shown such 
as names of hills, mountains, farms, villages, destination 
of roads and railroads, location of bridges, trestles, cul- 
verts, etc. The sketcher is governed only by consideration 
of the relative military importance of the points shown or 
omitted. 

On the sketch, directly under the description of the 
indicated point or object, should be shown its range. The 
range is either estimated or measured. (See Plate VIII, 
Fig. 2.) 

Elimination of unessentials : — The sketcher must re- 
member that he is busied in making a map, a military 
record which is to be used by others. Therefore he should 
ask himself constantly, "What value has this sketch at this 
moment to another person?" With this question before 
him the sketcher should be able to resist the temptation to 
draw unessentials, and so put down only data of value, re- 
cording such items in turn according to their imDortance. 



82 TOPOGRAPHY 

COMBINED SKETCHES 

25. The methods of combined sketching were developed 
at The General Service Schools several years ago and an 
interesting account of these methods, including the advan- 
tages to be gained in their use, can be found in the School 
Library in a book entitled "Individual and Combined Sketch- 
ing" by Cole and Stuart. 

26. To appreciate the advantages of the combined 
sketch, one must keep clearly in his mind the distinction 
between such a sketch and a combination of individual 
sketches. In the latter case a given area is assigned to 
each individual party and this area is sketched indepen- 
dently of all other parties. The results are then submitted 
to the draftsmen who adjust existing difference along the 
border line between the sketches in the office without any 
personal knowledge of the ground. Where a network of 
control lines exist with established elevations along each 
line, or sufficient time is available to establish such a net- 
work, each individual party may be assigned to an area 
bounded on all sides by the control lines and there is then 
no necessity for any two or more parties combining their 
work in the field. 

However, when there is no network of control or it is 
not sufficient to enable the draftsmen to make an intelligent 
adjustment and time is not available for the establishment 
of the necessary control, the advantages to be gained by 
requiring individual parties to adjust their work with ad- 
joining parties in the field is apparent. The following cases 
should be considered : 

1. Where certain control lines already exist but the control 
is not sufficient for adjustment in the office. 

2. Where no control lines exist. 

For example, certain railway surveys and road maps 
may exist giving a fair amount of flat control through the 
entire area. These roads or railways may then be made 
the boundary lines between parties ; and adjoining parties, 
working together along these lines, may establish joint ver- 
tical control and also adjust all horizontal features along 
the line. 



APPLIED MILITARY SKETCHING 83 

Or again, a single railway may be taken as a base line 
from which all parties start. 

The control may be so well established that it may not 
be necessary for some adjoining parties to adjust their 
work in the field while quite desirable for others to do so. 
In such a case, part of the sketch, may be a combination of 
individual sketches, but the other part becomes a combined 
sketch just as soon as adjustment is made in the field by 
two adjoining parties. 

27. In the case where no control exists, good results 
cannot be expected unless all the sketchers have had much 
experience, have worked together before, and the work is 
thoroughly organized. 

While either two or three sketchers may be assigned 
to one party in a position or area sketch, it is thought quite 
desirable that three be assigned if for no other reason than 
to keep in touch with the other two members of the party. 
If the man doing the actual sketching is worried all the 
time about finding another member of his party it is bound 
to detract from his efficiency, and failure of the two to 
get together at the outer limits of the sketch results in an 
incomplete sketch. 

28. The following method of making a position sketch 
is one that has been used by The General Service Schools 
in past years. It is not presented as the only method, as 
there are various ways of organizing the work to accomplish 
tha s:;me rssult. 

Assume that a general line has been sketched such as 
(C C). (Plate IX.) The position sketch is in charge of an 
officer designated as the topographical officer, who selects 
a base line such as (A-a-B), so that areas whose sides are 
perpendicular to the base line will include the general line. 
The total depth of area to be mapped will depend on the 
time and number of sketchers available. If the sketchers 
are skilled in their work and the terrain is not very diffi- 
cult, the entire area may be divided 'into parts one-half mile 
in length and two miles in depth and the work can be exe- 
cuted by fifteen parties in a day. Each small area, such as 
(a t s's) is assigned to a party of three, one chief of party 
and two sketchers. The topographical officer proceeds with 



84 



TOPOGRAPHY 




X 



APPLIED MILITARY SKETCHING 85 

all the parties to the point A where the most distant visible 
point of the base or control line, as (a), is pointed out to 
all chiefs of parties. Sketcher No. 1 of the first party, de- 
signated as party (A), determines the magnetic bearing of 
the line (A a) from which the magnetic bearing of the lines 
perpendicular to it is determined and begins sketching along 
line A A'. The chief of party A paces off a distance of a 
half mile along the line (A a). All topographers except 
sketcher No. 1 of party A follow the chief of party A. The 
elevation of the point A is determined by the topographical 
officer by an aneroid barometer. The aneroid barometer 
is preferable for this work, but if not available the eleva- 
tion of point A must be assumed and the relative elevations 
determined by the clinometer. This latter method is rather 
tedious if no known elevation can be seen, but is not so diffi- 
cult if sights can be secured on points of known elevation. 
When the chief of party A reaches the point (m) one-half 
mile distant from A, he halts with his No. 2 sketcher and 
No. 1 of the next party, designated as party B, and marks 
the point by a stake or selects some natural object in the 
near vicinity, such as a hill or fence post. 

The topographical officer then gives to the chief of party 
A the magnetic bearing of his right boundary and the ele- 
vation of the point (m) . The chief of party B starts pacing 
off the distance from (m) to a point (n) one-half mile dis- 
tant from (m), accompanied by his sketcher No. 1 and 
sketcher No. 1 of party C. The same process continues 
until (a) is reached where the bearing of the line (a B) is 
determined by the topographical officer and the number of 
wedge shaped areas is also determined by him. The wedge 
shaped areas are assigned to a selected party and the 
methods followed from (a) to (B) are similar to those de- 
scribed from (A) to (a). 

Meanwhile, at the point (m), sketcher No. 1 of party 
B in company with sketcher No. 2 of party A, sketches along 
the line (m m') and extends the sketch 300 yards on each 
side. It is in' material whether sketcher No. 1 of party B 
or sketcher No. 2 of party A does the actual sketching, but 
it should be done by the best sketcher of the two, the other 
acting as assistant. When these two have proceeded along 



86 TOPOGRAPHY 

the line (m m') for a distance of two miles, which would 
scale a distance of 12 inches on the map (assuming the 
scale of the map as six inches to a mile), the sketch is cut 
apart along the line (m m') , which is merely the cutting line 
of the sketch. It is not necessary that the sketchers follow 
the line (m m') on the ground, but they should so direct 
the traverse as to secure in the most convenient manner, 
reliable data for 300 yards on each side of the line (m m')- 
After the sketch is cut- apart each of the sketchers takes 
the part of the sketch assigned to his party, and from the 
point (m') sketches along the outer boundary of his area. 
In the meantime the chief of party B having run the care- 
ful traverse from (m) to (n), gets in touch with'both of 
his sketchers so that when the outer boundary is reached 
he may assemble the two without delay at a point about half 
way between (m') and (n')» When they assemble, the 
chief of party will have a plotted traverse showing the dis- 
tance between the parallel line (m m') and (n n') and the 
sketchers of his party will each have a sketch of a strip of 
topography 300 yards wide along each side of the area. 
These two sketches are then placed one over the other so 
that the distance betweerrthe outer edges at all points scales 
a half mile according to the scale of the sketch. A knife 
cut is then made down through the center so that there is no 
overlapping and the pieces secured in position by thumb 
tacks and rubber bands. The party then proceeds back to- 
ward the base or control line ^connecting up the contours 
and topographical features and adjusting differences. The 
sketch having been completed according to this method, will 
"at accurately along its edge with adjoining sketches on both 
sides, and all are ready for combination without any altera- 
tion whatever. Before turning in the sketch of his area 
at the appointed assembly place, the chief sketcher secures 
the two parts of his sketch in position with fasteners or 
binding tape. When turned in each sketch should also have 
a margin of at least an inch on each end so that they can all 
be pasted together without interfering with the portion on 
which the actual sketch exists. 

When turned in, it is only necessary to place all the 
sketches with their edges together in their proper relative 



APPLIED MILITARY SKETCHING 87 

positions and secure them at each end with binding tape. 
It is not necessary to trace this work for blue printing if 
the field work has been done properly. 

29. The question is principally one of organization. 
Each sketcher, upon being given his area, should be given 
also the co-ordinates of the points where he will meet the 
adjacent sketchers, the times he will meet them, and the 
common boundaries which they will sketch together. He 
must fulfill these appointments, no matter what the condi- 
tions of his work; afterward, if time permits, he may do 
other important Work on his area. 

30. In combined road sketching it is often impossible 
to know ahead of tfme just what are the co-ordinates of 
points on the connecting roads along which two sketchers 
are to meet ; in fact, it is often the case that it is not known 
that the road itself actually exists. In such cases, each 
road sketcher will be given bounding areas in which he is 
to sketch every road, these areas being made so that they 
will overlap several hundred yards. Each sketcher will 
then proceed to the limits of his area, and if it has been 
impossible to designate the co-ordinate at which he will 
meet the adjacent sketcher, and time of meeting, he will 
place a card in a conspicuous place on the side of the road, 
showing his ideas as to the co-ordinate of the card and his 
elevation (if elevations are being obtained). The adjacent 
sketcher will similarly sketch to his boundary; except that 
if he finds the card of the other sketcher, he will stop at 
that point and will endeavor to adjust his sketch to the co- 
ordinate and elevation of the other sketcher. If unable to 
do so, he will make a note on his sketch that this is the 
point where he found the card, defers any adjustment and 
proceeds with this work, it being unnecessary, however, for 
him to proceed farther along this same road. The overlap- 
ping of several hundred yards in the area designated to be 
sketched by each sketcher is necessary in order that the 
card of the first sketcher will surely be found by the second 
sketcher. 

The following is an organization which has worked 
well in peacetime, based on covering 3 main parallel roads : 



88 



TOPOGRAPHY 



Directors 

Principal Sketcher (main 
road) 

Asst. to Prin. Sketcher 

Asst. Sketchers (crossroads) 

Total enlisted (all 
mounted) i 

Officer in charge 



Party A 

Right flank 

road 



Party B 
Center road 



Party C 

Left flank 

road 



Total 



3 
3 
12 

21 
1 



31. In an unmapped country combined sketching may 
be utilized to furnish a rough map in the shortest practica- 
ble time. Without control of some kind the work of inde- 
pendent parties can never be made into an harmonious 
whole. The effect of the combination of parties is to supply 
in some degree the absence of control. In mapping exten- 
sive areas by independent parties before control is estab- 
lished the work of these parties is likely to be entirely 
wasted; if the combined sketch system is used the work 
may be adjusted to an accurate control when such control 
is obtained. 

32. Rates of Sketching: — A good sketcher, under 
average conditions, can sketch in one day: 

On foot : 

1 square mile of area. 
10 miles of road. 

Mounted : 

15 miles of road (in emergency 20 to 25 miles). 

33. The following data is of use in reconnaissance work : 
Water — Approximate daily requirements : 

1 gallon per man on march. 

5 gallons per man in camp. 

6 to 10 gallons per animal on march and camp. 

(The above figures apply to water taken from streams, 
where animals are watered at the streams, and cooking 
water carried. In estimating the daily supply for perma- 
nent or semi-permanent camps, where water is piped to 
kitchens, bath houses, etc., the requirements will be 25 to 
30 gallons per man and 10 to 15 gallons per animal, depend- 
ing on climatic conditions.) 



APPLIED MILITARY SKETCHING 89 

Estimating quantity of water in stream: BxDxVX 
10,800=gallons in 24 hours. B=average width, D=aver- 
age depth, V=average velocity (all in feet). 

34. Practicability of slopes. Slopes from 0° to 5° are 
practicable for maneuvering all arms, singly or combined. 

On slopes from 10° to 15° all arms can be moved up or 
down. 

Slopes from 15° to 30° are practicable for small de- 
tachments only. 

On slopes from 30° to 45° foot troops can move with 
difficulty. 

War material can be dragged up any slope. 

Slope fractions Degrees Operations 



1/50 
1/20 
1/12 


1 
3 


1/10 


6 


1/8 

1/7 
1/6J 


7 
8 
9 


1/6 
1/4 
1/3 
1/2 
1/1 


14-15 
18| 

,26 

45 



Maximum for railroads. 
Maximum for first-class roads. 

Practicable for all arms. Somewhat difficult for cav- 
alry to charge descending. 
Maximum for cava'ry charge in mass ascending. In- 
fantry in close order descends with some difficulty. 
Cavalry can descend at a trot. 
Not practicable for heavily loaded vehicles. 
With few exceptions it is impossible for heavily 
leaded trucks to climb grades exceeding 16 per cent 
(about 9°), even when the road surface is hard 
ti . ood condition. 
Fie'd artillery can no longer maneuver. 

mm up to which all arms can move. 
i ight vehicles can ascend. 

■ .' and mules can ascend or descend. 
Foot troops can ascend or descend aided by bands. 



35. The minimum width of usable roadway for a two- 
way road is 18 feet. 

36. Fords, Practicable Depth : 

2 to 3.5 feet deep for infantry. ~] 

4 to 4.5 feet deep for cavalry. [ Depending on current and 

3 feet deep for artillery. nature of bottom. 
2.3 feet deep for wagons. 

37. Strength of Ice: 

Three inches thick will support small groups of men. 

Four and one-half to 7 inches thick will support cavalry 
and light guns. 

Eight to 12 inches thick will support heavy guns and 
wagons. 

38. Stream Flow: 

Velocity in miles per hour=0.7 of velocity in feet per 
second. 



90 . TOPOGRAPHY 

Practical Exercises in Applied Military Sketching 

See any of the recent problems at The General Service 
Schools, Fort Leavenworth, Kansas. Each of these prob- 
lems required a certain kind of sketch under certain military 
conditions. The results of the problems showed that nearly 
all officers possess a general knowledge of the methods of 
sketching, but not so many possess the ability to show in a 
limited time the military features required by a special 
sketching mission. 



CHAPTER V 

Airplane Mapping 



1. Aerial photography has reached a stage of develop- 
ment where it is of distinct value in military operations both 
in providing information of enemy works and operations, in 
reconnaissance work, and in furnishing data on which to 
base new or revise old topographic maps. 

Owing to the fact that good topographic maps already 
existed of the western battle front in the World War,' no 
new surveys of it had to be made and aerial photography 
was principally devoted to detecting enemy works and evi- 
dences of his operations. The information thus obtained 
was supplied to organizations principally by making addi- 
tions to the existing maps and by distributing great num- 
bers of the photographs. 

Under these conditions, airplane mapping, which had 
been developed to some extent in the United States and 
abroad before the World War, did not receive as much at- 
tention as the intelligence use of photographs, although the 
Germans claim to have mapped large areas of terrain on the 
eastern front by airplane photography. Since 1917 the 
Corps of Engineers, the Air Service and the Geological Sur- 
vey have been working conjointly on the development of 
methods and instruments for airplane mapping and have 
brought the subject to a point of practical application to 
military mapping. 

The use of aerial photographs is still limited to only 
a portion of the work of complete topographic mapping; 
primary control and contouring of the ground are still ne- 
cessary, and the efforts made so far represent pioneer work 
in which the influence of the experimental stage enters to 
a high dgree. 

2. Aerial photography has four distinct and valuable 
uses in military operations: 

91 



92 TOPOGRAPHY 

(a) In map making. 

(b) In reconnaissance. 

(c) In supplementing battle and operation maps, to guide 

organizations in an attack. 

(d) To give information of enemy works and operations. 

GENERAL LIMITATIONS ON AERIAL PHOTOGRAPHS 

Application of Aerial Photography to Military 
Sketching 

3. An aerial photograph is a photograph of the ground 
taken from the air. It may be either oblique, or vertical. 
An oblique photograph is one taken from a low-flying ma- 
chine or captive balloon, with the axis of the camera making 
an acute angle with the ground. It is used for giving a 
panoramic view of the ground, and is of little use in map- 
ping. A vertical photograph is one taken with the axis of 
the camera perpendicular (or approximately so) to the: 
surface of the ground. It is usually taken in war time from 
an altitude of from 8000 to 15000 feet. For the best re- 
sults, photographs taken in time of peace are usually taken 
under 6000 feet. 

In addition to its other uses, the vertical aerial photo- 
graph is used in mapping. Such a photograph has the fol- 
lowing advantages: 

(1) It is the best means of securing fresh topographical in- 
formation about territory in enemy possession. 

(2) It is sensibly free from errors due to the personal equa- 
tion of the topographer. 

(3) It is the most rapid means of securing such topographical 
information as is shown on the picture. 

(4) It is the least expensive method (in human life) for se- 
curing a record of our own works in territory subject to enemy 
fire. 

The vertical aerial photograph has the following dis- 
advantages : 

(1) As the position of the camera and its orientation at the 
moment of exposure is never accurately known, aerial photographs 
must be employed without these data. No practicable means of 
determining them in the office has yet been devised. 

(2) It is extremely difficult to hold the camera directly ver- 
tical, and slight deviations from this position cause considerable 
distortions in the record. 

(3) No data as to the relative elevations of objects on the 
ground can be secured from the photographs except some slight 
information from the images of the shadows. 

(4) Objects hidden to the observer in the machine, whether 
by clouds or by overlying terrestrial objects, such as forests, etc., 
are equally hidden in the photograph. 

(5) All aerial photographs are subject to special errors of 
distortion. 



AIRPLANE MAPPING . 93 

The most important advantages are the completeness 
and accuracy of detail and the speed of getting features 
which are tedious to draw or difficult to reach. 

Speed of Work 

4. A single sketcher with good control can put in the 
detail in diversified country of about one square mile per 
day. 

A single photograph from a tri-lens camera taken from 
an altitude of 10,000 feet can cover an area of about 10 
square miles. Due to the necessity, explained below, of 
taking a large number of overlapping photographs, the area 
covered by a single plane in one flight is not much over 
35 square miles. 

Actual cases : 

An area 15 x 20 (300 sq. miles) required 22 strips of 33 photos 
each (7" x 9") or 726 photos. 9 hours flying time for photo- 
graphs or 4 flying days. 

Atlantic City Mosaic — 35 sq. miles. 
Flying time— 2a hours. 
Total time in field — 4 days. 
Time in laboratory and in assembling mosaic — 2 weeks. 

Camp Benning — 150 sq. miles. 
Flying time — 10i hours. 
Number of photos — 619. 

Time spent in field to take and finish photos— 41 days. 
Time spent in assembling mosaic — 1 month. 

In the 8th Corps Area 17,000 square miles were map- 
ped between April and August, 1921. The personnel con- 
sisted of seven officers, ten enlisted men and two civilian 
photographic developers. Four planes were operated. 

5. The cost of topographic surveying without airplanes, 
excluding control, will average about $50.00 per sq. mile. 

The cost of getting topography by airplane photography 
after control has been obtained by other means averages 
about $10.00 per sq. mile. This cost is not comparable with 
the above as no data on vertical relief is obtained. 

The comparative cheapness of the airplane photograph 
method is an advantage since most maps, even those for 
military purposes, are made in time of peace, when cost 
has to be considered. 



94 TOPOGRAPHY 

Disadvantages 

Principal disadvantages in use of airplane photography 
in mapping are due to the lack of control and errors of dis- 
tortion. 

Lack of Control: — No method has yet been devised 
of registering the positions of the airplane when the pho- 
tograph is made. 

Control points, which will register in a photograph, 
must be established by ordinary methods of terrestrial sur- 
veying. Without control previously established airplane 
photographs though they may be valuable for reconnais- 
sance purposes, are useless for map making. 

Distortion : — The principal errors of distortion are 
due to inclination of the camera and to differences of eleva- 
tion in the terrain. 

No method has been devised for keeping the axis of 
the camera vertical or for registering the amount of in- 
clination. 

If the axis is not vertical the photograph will be dis- 
torted exactly as the photograph of a tall building taken 
from near its base. 

Distortion due to relief arises from the fact that points 
at different elevations, equally distant from each other, will 
not be projected at equal distances on the photographic 
plate. A simple geometric figure will show this. 

Uses of Airplane Photographs 

G. Reconnaissance: — Airplane photography has a 
very valuable field of usefulness in the reconnaissance of 
roads, streams, and large uncharted areas where the prin- 
cipal object is to get the character of the road or terrain, 
and the lack of control is unimportant. 

With the ability to photograph a strip of country from 
2 to 6 miles in width and from 50 to 75 miles in length, it is 
possible to make an excellent road reconnaissance ahead of 
a marching column. 

No absolute control is needed other than the road fol- 
lowed or towns passed over. The photographs will show 
the width, and possibly the character of the road; the 
bridges, whether standing or destroyed, width of streams at 



AIRPLANE MAPPING 95 

crossings, fords along side of roads and the general nature 
of the topography for a distance of from 1 to 3 miles on 
each side of the road. 

Flying can be done in the morning, photographs devel- 
oped and mounted in the afternoon and ready that night for 
issue to advance guard or column commanders. A map 
would be preferable, but the making of a map from photo- 
graphs requires several days. 

A number of valuable route reconnaissance maps have 
recently been made in the 8th Corps Area. In some cases 
the flight followed a railway, the survey notes of^which were 
available. In other cases a rough survey of the route to be 
followed was made by using a compass and speedometer. 
In other cases the mosaic was controlled simply by different 
towns, the location of which was known. 

A reconnaissance of a stream will show its width, char- 
acter of banks, whether steep or wooded, and location of 
fords. 

A reconnaissance of large unmapped or incompletely 
mapped areas, such as might be found in Mexico, will give 
a good idea of the general character of the terrain and will 
be valuable even though the exact location of the various 
features cannot be determined. 

7. For Battle Use : — Vertical and oblique photographs 
issued to organization commanders in conjunction with bat- 
tle or operations maps are useful aids in orienting and 
guiding organizations in an attack. 

About 40,000 such photographs were issued by G2, 
First Army, for the St. Mihiel attack down to and including 
platoon commanders. That their use was not more success- 
ful was due to lack of instruction in their interpretation and 
use, and to lack of time. 

Issuance of photographs to small units is too much of 
a detailed task for the army. They should be supplied by 
the division. 

8. Map Making: — Airplane photographs are used in 
mapping to correct and revise old maps, fill in existing maps 
and make new maps. 

In the last case, making new maps, some existing map, 
i.e., some control is absolutely necessary. 



96 TOPOGRAPHY 

9. Relief: — No practicable method has yet been dis- 
covered of getting elevations from vertical photographs. 
The Germans and French have developed complicated meth- 
ods involving minute measurements but they are not prac- 
ticable for military purposes. The general character of re- 
lief, however, can be determined from stream lines, shad- 
ows, location of woods, bends in roads and curves in rail- 
ways. 

10. Control: — It is necessary to have a guide map on 
which courses to be flown to obtain the photographs can 
be marked. From the air the pilot identifies points on the 
terrain which correspond with the courses and uses them 
to maintain proper directions during flights. It is generally 
necessary in order to insure that no gaps occur and to re- 
duce distortion due to inclination, to have the photographs 
overlap on all sides. The prints are then brought to the 
same scale, if necessary, fitted and adjusted to the control, 
the overlapping parts cut away and the remainder mounted 
together to form a mosaic. 

11. Cameras: — The cameras in use in our service are 
a single lens automatic camera and tri-lens non-automatic. 
The latter consists of three cameras, one central and two 
side cameras inclined in opposite directions at an angle of 
35 degrees to the central camera. This camera was designed 
especially for mapping purposes and has a field about three 
times as large as that of the single lens automatic type 

12. Transforming: — The side pictures of an inclined 
lens camera are distorted with reference to the central pic- 
ture. By projecting the negatives onto a plane making the 
same angle with the negative that the side cameras make 
with the central axial camera, the resulting prints will be 
the same as though the axes of all the cameras were paral- 
lel. This process is called transformation. If it were pos- 
sible to register the tilt of a camera, distortion due to lack 
of verticality could be eliminated by transformation. 

Interpretation and Restitution 

13. A photograph print furnished to an organization 
must be interpreted : i.e., some one must decide what the 
various objects shown on the photographs really are. The 



AIRPLANE MAPPING 97 

interpretation of houses, open roads, schools, rivers, boun- 
daries of woods and swamps, trace of open trenches, etc., 
usually presents no difficulty to any topographer. On the 
other hand, the interpretation of objects hidden by other 
natural objects, such as roads in a forest, etc., is frequently 
very difficult. The interpretation of military features, 
which have been specially prepared on the ground to resist 
interpretation (camouflaged) involves difficulties which can 
usually be solved only by experts, and is a problem in mili- 
tary intelligence, and not in topography. 

The location on a map of the various features on the 
photograph, after they have been interpreted, is termed 
restitution. Restitution is a branch of topography. Where 
restitution is done in great haste, with a view to getting 
information into the hands of troops rapidly, it is a branch 
of sketching. 

14. Control of Restitution: — Theoretically, given 
the elevation at which the vertical photograph of a flat sur- 
face was taken, and the optical characteristics of the camera 
(i.e., the focal length) the scale of the photograph, con- 
sidered as a map, could be calculated. Since the altitude of 
exposure is known only approximately, the axis of the cam- 
era is rarely vertical and the surface photographed is never 
flat, an accurate calculation is impracticable. In sketching, 
the scale would be determined by measuring the straight 
line distance between two control points, and comparing it 
with the actual horizontal distances between these points 
on the ground. Even this scale will be inaccurate, owing 
to errors of distortion. It is, however, usually accurate 
enough for sketching purposes. Several control points if 
available should be used to obtain an average value for the 
scale. 

The selection of control points should be made from the 
best available existing map of the area photographed, and 
those used in determining the scale should be chosen as 
near the centre of the area as possible. Because their 
images are usually definite on the picture and their loca- 
tions are generally accurate on maps, pronounced features 
along railroads and roads such as crossings and roadforks 
are the most satisfactory control points. It is impossible 



98 TOPOGRAPHY 

to use a restituted photograph in topography, unless at 
least two control points can be located. 

15. Methods of Restitution: — Owing to errors of 
distortion which make the scale of a photograph variable 
in different parts of the picture, it is insufficient merely to 
reduce or enlarge the picture to the scale of the sketch. 
There are three methods of transferring data from the pho- 
tograph to the map, the graphical, the optical, and the pho- 
tographic. Only the graphical method is adapted to sketch- 
ing. 

In the graphical method four control points are se- 
lected on the photographic print which can be identified on 
the map. These points are connected by straight lines form- 
ing a quadrilateral. By drawing the diagonals, four tri- 
angles are formed, and these triangles can be again divided 
into as many small triangles as will be found necessary for 
the amount of detail desired. The same number of lines 
and figures must be drawn on both photograph and map. 
The features on the photograph are then transferred to the 
map. 

Knowing the scale both of the map and the photograph, 
compilation work is comparatively simple. The sketcher 
measures the perpendicular distance, on the photograph, 
from a point to the nearest triangle boundary, and the dis- 
tance along the triangle boundary to the nearest intersec- 
tion. He converts these distances to the scale of the map, 
measures them back in reverse order, and locates the point 
on the map which corresponds to the point on the picture. 
After a few points have been thus located, the remaining 
features in the triangle can usually be drawn in freehand. 

16. Interpretation : — In examining an airplane pho- 
tograph it should be held so that the shadows fall toward 
you and also away from the source of light (lamp or win- 
dow) . If it is held so that the shadows fall away from the 
eye the relief is apt to appear reversed — a cut will look like 
a fill. Having the source of light in the same relative posi- 
tion as the sun when the negative was exposed will assist 
in bringing out the relief. 

Interpretation is facilitated by a study of a map of the 
terrain covered by the photograph. If none is available, try 



AIRPLANE MAPPING 99 

to get a map and photographs of adjacent similar terri- 
tory. 

The Use of Airplane Photographs to Obtain Informa- 
tion of Enemy Works and Operations : 

17. This use of air photos is commonly considered an 
intelligence function though, as a matter of fact, it is largely 
a matter of map making. The restitution of enemy works 
for purposes of artillery fire, planning attacks, etc., which 
may be considered a tactical use, is trfie mapping. The 
comparative study of the restituted works to discover 
changes in appearance of front line works, and evidences of 
concentrations, etc., in rear areas, a strategic use, from 
which the enemy's intentions and operations may be de- 
duced, is intelligence work. 

18. In interpreting photographs of enemy works the 
expert depends on four main characteristics : 

(a) Shadows, showing- especially trenches. 

(b) Marks of use, such as tracks, blasts, etc. 

(c) Marks of construction, such as spoil banks, felled trees, 

etc. 
(cl) Differences, as compared with previous photographs. 

The camouflage operator endeavors to nullify such 
characteristic features. He does not attempt to render the 
objects invisible, but he does attempt to make the object 
cause no change in the appearance of the terrain. He uses 
nets to overcome the shadows, covers up tracks and blasts 
or prevents the making of same, covers or disguises spoil 
banks, etc., and endeavors to prevent any differences of ap- 
pearance in the terrain. 

However, although camouflage operators covered the 
object, there are certain characteristic features as discussed 
below, which show certain enemy activities ; and careful 
reading of aeroplane photographs gives results of very great 
military assistance. Plates III and IV show an aeroplane 
photograph actually taken in France, and its interpre- 
tation. 

19. The degree of certainty with which enemy batteries 
may be located by aeroplane photographs depends on the 
perfection of the camouflage and the character of the ter- 
rain. Verified locations in France during the World War in- 



100 



TOPOGRAPHY 




Plate III 



AIRPLANE MAPPING 



101 




'Wire 
^'\ZA859 JO 9/6 8000' Lens JO' 

PL.te IV 



102 TOPOGRAPHY 

dicate that the percentage of batteries located by this means 
varied from 20% to 70% of those present. 

In reading airplane photographs, there is great diffi- 
culty in determining the meaning of certain signs on the 
photograph. Actually, it is often impossible to interpret 
the meaning of certain signs as seen on the photograph ; 
but the specialist who is engaged in interpreting the photo- 
graph has at hand all of the information concerning the 
particular section, such as reports of fire of batteries from 
a certain vicinity, the reported presence of machine guns 
in a wood, the presence of heavy guns in a ravine. By com- 
bining this information with a careful study of the indefin- 
ite signs on the photograph, it is possible to come to fairly 
correct results. 

20. Aviation Fields: — Hostile airdromes may be re- 
cognized on photographs by the following indications : 

(a) Hangars. 

(b) Preparation of the ground. 

(c) Landing "TV or small smoke fires, giving the direction 

of the wind. 

(d) Machines on the ground. 

21. Batteries: — Casemated or underground battery 
emplacements are always easy to distinguish on the photo- 
graphs, on account of the shadows from the projections, 
provided the shadows are not hidden by camouflage. 

The different color of excavated earth in comparison 
with the ground immediately around an emplacement makes 
the spoil very noticeable. The enemy knows that, as the 
importance of a position may be determined by the amount 
of excavated earth, it is desirable to transport all earth to 
a distance before scattering it. Gun positions very care- 
fully camouflaged, have been discovered because the cut turf 
was noticed in the territory immediately surrounding them. 
In the winter time the enemy has to throw snow over the 
uncovered section of ground. 

In wooded country, especially if the woods are of any 
extent, batteries are difficult to locate with accuracy owing 
to the fact that just when conditions are most favorable 
for air photography (i.e., the spring and summer), the leaves 
and natural cover are thickest. Camouflage with fresh 



AIRPLANE MAPPING 103 

branches and undergrowth is a simple matter, and tracks 
which can be seen entering a wood are soon lost inside it. 

An orchard or a hedge can completely conceal a bat- 
tery if the occupants take sufficient precautions to avoid 
circulation marks, blast marks, etc. 

Pieces installed in caves or in the midst of partially 
ruined houses blend with the white ruins and it is difficult 
to distinguish them. 

22. When batteries are forced to retire, the enemy 
sometimes constructs emplacements of the normal type in 
the new positions, but during extensive operations it is 
common for guns to come into action in the open without 
protection of the guns themselves or for the battery per- 
sonnel. In this case, one would expect to find the battery 
near a road or in a position where the natural features of 
the ground give a certain amount of protection. 

23. When the tactical situation necessitates the rapid 
installation of batteries on terrain that presents no cover, 
the enemy sometimes neglects to conceal them. They frankly 
accept the hardship of fire and dispense with all attempts 
to assure efficient protection for the personnel and materials. 
If the photograph is taken at a great height, however, the 
battery itself is rarely discernible in the photograph of 
the target. At a lower altitude, the effect of camouflage 
is the same, viz., the battery cannot always be discerned 
directly. 

24. Battery positions are indicated directly by the regu- 
larity of the work, the blast marks, and the smoke. The 
enemy avoids placing his shelters in regular groups, and 
tries to eliminate abrupt changes in the angle of slope be- 
tween the camouflage and the surrounding ground, and to 
eliminate conspicuous shadows. All regular geometrical 
forms are avoided as much as-possible in the construction of 
the works. The blast of a piece traces a clear, very char- 
acteristic mark in front of the muzzle of the gun, especially 
if it is firing at a low elevation. When the snow is on the 
ground, it is particularly difficult for the enemy to cover 
the area melted by the heat of the blast. To avoid blast 
marks in dry weather, the guns are sometimes placed where"' 
they will fire across a road or under a tree. 



104 TOPOGRAPHY 

25. Battery positions are indicated indirectly by marks 
on the surrounding ground, of which the principal are tracts 
and paths. Practically the first thing that is noticed on the 
photograph is the system of tracks. Most often the artil- 
lery is revealed by the radiating tracks. Tracks which end 
abruptly in a fan-shape are clearly discernible. At each 
track end, there appear clearly emplacements in semi-cir- 
cular form. From this it results that the approach roads 
may be effaced to at least 300 meters in rear by plowing 
or harrowing, or other means. 

Because of the number and importance of tracks the 
enemy makes an extraordinary attempt to suppress the 
traces. A common means of hiding tracks made by men 
is to make the troops follow the borders of cultivation — the 
perimeter of fields. Every path that cuts across a field in 
any one direction shows up conspicuously on the aeroplane 
photograph, and in following its trace, we can arrive at the 
work to which it leads. 

A feature with batteries in exposed positions is a 
covered trench leading from an adjacent road or trench, 
enabling personnel and ammunition to enter the battery 
without leaving tracks above ground. 

When a path stops abruptly or becomes narrow when 
it has been broad, we find, in the vicinity of the point where 
it changes form, something whose presence necessitates im- 
portant circulation. If the nature of the ground and the 
distance from the front are favorable for an artillery posi- 
tion, we report the possible presence of a battery. 

26. It is evident that on photographs false batteries 
are at the very first glance easy to distinguish from real 
positions, if care is not taken. This is especially true when 
it is considered sufficient to build false emplacements, and 
leave the surrounding ground as it is, especially behind the 
position so that the false position on the photograph ap- 
pears to be deprived of movement. That is why it is strictly 
necessary that, behind each false battery, tracks should be 
kept fresh by making supply trains pass over them from 
time to time, as often as possible, preferably after a rain, 
and in a direction previously decided upon. A haphazard 
circulation of traffic behind the position without following 



AIRPLANE MAPPING 105 

a pre-determined road does not deceive the enemy suffi- 
ciently. Smoke is sometimes produced to simulate kitchens, 
false telephone lines are installed, and blast marks made. 

At the end of an existing wagon road, as often as pos- 
sible, a false battery with radiating wheel tracks is installed. 
The foot path leading from the false battery to the position 
occupied need not be direct. 

The enemy construct few dummy batteries. Those that 
exist are generally recognized by the too clear indication 
of the blast marks, and of the artificial paths. 

However, one finds in the enemy lines many reserve 
emplacements, for the most part unoccupied, which serve. 
the same purpose as false batteries. 

Machine Guns may be looked for : 

(a) Where an angle occurs in the trench system, or a trav- 
erse is constructed so as to bring fire to bear on the flank. 

(b) Within easy reach of a communication trench, with dug- 
outs for the team close at hand. 

The covered emplacement may be discovered by a V- 
shaped mark in the forward edge of the parapet, where the 
latter has been cut away to allow the gun to traverse. At 
the back of this "V" or close beside it in the trench, if the 
emplacement is entered from the side, may be found a dark 
spot similar to a dugout entrance. 

The open emplacement takes the form of a square tray 
or concrete platform let into the parapet. It varies in ap- 
pearance according to the altitude of the sun, and may 
show up either as a white mark with a dark edge or as a 
comparatively dark square. The latter is hard to distin- 
guish from the many dark cuts in the parapet, which may 
be sentry posts or firing recesses. 

Outside the trenches, the search requires a minute ex- 
ploration of the whole terrain in which tactical reasoning 
plays an important part. 

Railways: — Light railways usually follow contours 
and defilading ground, and may sometimes be discovered 
by the fact that they lead into trenches which have no 
traverses and sharp corners. It is very difficult to establish 
the presence of light railway along a road, as it is generally 
constructed near a ditch and under trees. The railway 



106 TOPOGRAPHY 

may often be discerned at corners of the road and under 
roads, where it is necessary for the lines to leave the road 
or to make a more gradual curve. 

Standard gage roads are never successfully camou- 
flaged, but sidetracks for the cars are placed from 500 to 
1000 meters from the nearest freight yard to distract at- 
tention from the important unloading point. 

Sometimes the narrow gage railways (particularly the 
0.60-m.) are camouflaged by tunnels or roofs of branches, 
but result is not deceptive. 

The railway spurs that lead from a main line to allow 
the long distance railway artillery to fire, are camouflaged 
with special care. Before and after the spur is in use the 
tracks are often covered with dirt covered tarpaulins, the 
excavation in the bank is concealed with a slanting screen 
of branches, a number of false spurs are constructed to dis- 
tract attention, and the gun and carriage are carefully con- 
cealed beneath a large screen of nets with interwoven 
branches. 

27. Reserves: — One should distinguish between the 
troops in reserve, who are kept immediately behind the com- 
bat position or near the second position, and the troops 
in rest, in the re^-r. 

The supports, or reserves, are placed : 

In shelters opening along trenches or communication trenches. 
In shelters hidden, opening behind a feature of the terrain 

or sunken road. 
In groups of shelters forming real caverns in the open or in 

the woods. 
In old quarries. 
In tunnels. 
In organized caves (rarely). 

The only indications of a reserve emplacement are: 

The spoil, sometimes transported some distance away by a 

narrow gage road of 0.60m. or 0.40m. 
The circulation. 

The paths leading up to the position. 
The entrances, ventilation, chimneys, etc. 

(b) Troops in rest are found: 

In camps in the open, but defiladed from terrestrial and 

balloon observation. 
In camps in the woods. 
In villages. 



AIRPLANE MAPPING 107 

The indications are : 

The presence of barracks. 
Paths disappearing into woods. 
Paths for training horses. 

Proximity of exercise grounds, works for hand grenadiers, 
firing positions. 

28. Roads, Paths, Tracks, Etc.: — A study of tracks 
will often reveal the following points: 

Roads in use (by parallel or divergent tracks in their vicin- 
ity). In wet weather it is possible to distinguish the 
character of the road, whether paved or unpaved. 

The main communication trenches in use (by tracks running 
alongside, made by carrying parties at night) . 

Many tracks on both sides of trenches often indicate that 
trenches are in bad condition. 

Dumps. 

Billets and hutments (especially in woods). 

Active battery positions. 

Headquarters. 

Wire which is almost invisible, and gaps through it. 

Patrol paths. 

Observation posts. 

In villages, houses which are important centers. 

Advance listening posts. 

Fortified shell holes. 

In quiet parts of the line, the appearance or gradual 
disappearance of tracks will often give valuable information 
as to the enemy's activity in any particular locality. 

During the artillery preparation new tracks leading to 
a group of dugouts under bombardment are sure signs that 
the dugouts have not been absolutely destroyed or that 
they have been reoccupied. 

The appearance of tracks varies with weather condi- 
tions; sometimes they show up as white lines of varying 
thickness, sometimes as darker ones. 

29. Organized Shell Holes are of two distinct forms : 

(a) Shell holes, real or artificial, placed in echelon, in stag- 
gered formation surrounding machine gun emplacements outside 
the trenches. 

(b) Shell holes, often square, which often seem shallow, 
grouped in pairs, usually on high ground for drainage purposes. 

These organizations, which one can only study on large 
r-~ale photographs, are disclosed by the spoil which is some- 
times scattered in nearby holes, by the organization itself, 
by tracks, by the material left on the side or in the holes, 



108 TOPOGRAPHY 

by a visible entrance to a shelter at the bottom, or by a 
segment of communication trench prolonged underground. 

30. Shelters are indicated by the following character- 
istics : 

During construction: 

(a) The digging and the spoil. The excavation, often con- 
cealed by camouflage, reveals concrete shelters, the spoil from 
which is visible around the hole or carried off some meters to. 
the rear to form a large pile, or transported some distance by 
narrow gage. The spoil from a mine-gallery shelter is gen- 
erally disposed around the two entrances (which appear as black 
points visible at the end of the works). 

(b) By the narrow gage railway transporting the concrete. 

After construction: 

(a) Traces of the entrance (shadow or small notch in the 
parapet or bench). Often the entrances of one concrete type 
are between two traverses. 

(b) The ventilation chimneys. 

(c) The trace left by the narrow gage railways. 

(d) The spoil and sometimes the path made by its evacua- 
tion. 

Any unusual amount of spoil should be scrutinized care- 
fully, as it may indicate subterranean work. 

31. Supplies: — Dumps are discovered by the piles of 
material, tracks, roads or even railways leading to the 
dumps. 

Supply centers are determined, first, by deciding as to 
their proper location, second, by searching the vicinity for 
railways, roads, tracks, etc. 

Supply depots will be found where standard gage rail- 
way changes to narrow gage ; also at switches, warehouses, 
etc., along tracks. 

32. Trenches are identified on photographs by the 
characteristic line of traverse and fire-bays, showing up as 
dark and light lines, varying with the direction of the light. 

Dummy or incomplete trenches can be identified by the 
comparative absence of shadow. 

The extent to which spoil on the parapet or parados is 
conspicuous depends on the nature of the soil and the new- 
ness of the work. 

33. Trench Mortars : — Light trench mortars are often 
fired from open emplacements to allow a rapid change of 



AIRPLANE MAPPING 109 

position, and it is difficult to distinguish the appearance of 
these emplacements from that of latrines and dump pits. 
One difference, which is by no means universal, is that 
trenches leading to trench mortar emplacements are more 
often zig-zag or traversed than are trenches leading to 
latrines. 

Medium and heavy trench mortar emplacements are 
casemated and much more conspicuous. They can gen- 
erally be recognized by an almost square, dark mark in the 
center of a mound or a ring of earth. This square mark 
is the top of the funnel up which the mortar fires, and 
differs in appearance according to the angle of light. 

34. Barbed Wire shows up on a photograph as a broad 
line varying in tone from light gray to almost black, accord- 
ing to the newness of the wire and the contrast with the 
color and texture of the ground. The tracks made by work- 
ing parties are often visible along either side of a belt. 

As ground becomes cut up by bombardment, wire be- 
comes increasingly difficult to distinguish. . 

The absence of signs of wire on a photograph must 
not necessarily be taken to mean that no wire exists. Oblique 
photographs will often reveal wire which does not cast 
enough shadow to show up on a vertical photograph. 

Wire is very often the earliest indication of a new line 
of defense. 



CHAPTER VI 

Mapping Large Areas 



1. There are many organizations engaged in mapping 
for the United States. The following is a list of them : 

U. S. Coast and Geodetic Survey. 

U. S. Geological Survey. 

General Land Office. 

Topography Branch, Post Office Department. 

Bureau of Soils. 

U. S. Reclamation Service. 

Bureau of Public Roads. 

Bureau of Indian Affairs. 

Mississippi River Commission. 

U. S. Lake Survey. 

International (Canadian) Boundary Commission. 

Forest_ Service. 

U. S. ilydrographic Office. 

Corps of Engineers, U. S. Army. 

2. The .Corps of Engineers of the .United States Army 
is in charge of the map work for the United States Army, 
because of the army regulations which prescribe, among 
their duties—* 

"Reconnoitering and surveying for military purposes, in- 
cluding the laying out of camps; the preparation of military 
maps of the United States and its possessions, including co-opera- 
tion with other Government and private agencies, and in field 
operations of maps of the theatre of operations." 

3. It will be noticed that these regulations state that 
the Corps of Engineers will co-operate with other Govern- 
ment and private map agencies. As a result of this co- 
operation, particularly with the Coast and Geodetic Survey 
and with the Geological Survey, the Corps of Engineers 
has been able to obtain maps of our coast lines, borders and 
interior localities. These maps will be very useful in case 
of hostilities. 

4. In addition to the map making organizations men- 
tioned above, the Corps of Engineers has been assisted by 
the Army through progressive military maps ; however, the 

110 



MAPPING LARGE AREAS 111 

results obtained by this work vary so greatly that the gen- 
eral advantage is doubtful. 

Present Status as to Maps 

5. On the eastern coast there are fairly good maps from 
Maine to Jacksonville, Fla., covering the whole section of 
the coast line, except the coast of North Carolina. 

6. On the western coast, there are fairly good maps 
covering every section of the coast except the mountainous 
country west of Puget Sound and this would not be of any 
military importance. There is a map of the northern coast 
line of this section, which is the only part that would be 
useful. 

7. Along the northern boundary, there are fairly good 
maps, covering about 50 per cent of the border ; in the other 
50 per cent there are still unmapped a few small sections 
and the large sections of Maine, Michigan, Minnesota and 
North Dakota. 

8. Along the southern boundary, there are fairly good 
maps, except of that portion of Arizona west of Nogales ; 
and as this is a desert country, it is not deemed of great 
importance, though efforts are being made to map it in the 
near future. Incidentally, there are maps of certain small 
areas across the boundary in ,Mexico, but these maps are 
not reliable. 

9. It is noticed on looking over the portions of the 
country which have been mapped by the Geological Survey 
that certain states such as West Virginia, New York, Massa- 
chusetts and Pennsylvania are completely covered, whereas 
Michigan and Louisiana have practically not been mapped 
at all by the Geological Survey. This is due to the fact 
that the Geological Survey has generally an appropriation 
which must be aided by appropriations by the state. In coal 
states, such as West Virginia, the state has made the nec- 
essary appropriations. 

10. In Hawaii, there is an excellent map of the Island 
of Oahu to the scale of 1 : 18,000 ; this will be made 1 :20,000. 

11. In Alaska there are practically no military maps. 
In Panama, the Coast and Geodetic Survey have published 
reliable charts of the Pacific and Atlantic coasts on either 



112 TOPOGRAPHY 

side of the Canal. War Department maps, scale 1 :62500, 
have been made of the coasts and waters adjacent to each 
entrance and maps on a scale of 1 :21120 are available cov- 
ering nearly the entire Zone, and considerable territory ad- 
joining it on each side of the Isthmus. 

12. In the Philippines, the United States Army has 
mapped about f of the Island of Luzon. The only unmapped 
portion consists of inaccessible mountains and useless coast 
line on the east coast. Considerable work has been done 
towards mapping the rest of the Philippine Islands. This 
was indexed by the same system as the Progressive Mili- 
tary Map of the United States. The scale to be used was 
1:62,500 and 1,125,000 at first; but most of the sheets seem 
to have been made to scale 1:63,360 (1 inch) or 1:126,720 
(i inch). 

Map Sheets and Scales 

13. The earth is round and the map sheets are flat. 
One cannot show accurately even a small portion of the 
round earth on a flat sheet. However, there is a system 
called "polyconic projection," wherein the surface of the 
sphere is projected on the surface of a cone tangent to the 
sphere and the cone is rolled out, or developed, on a plane. 
The distortion is small for points near the circle of tan- 
gency; therefore to avoid great distortion and still be able 
to represent considerable surface of the sphere a number of 
cones tangent along adjacent circles of latitude are used, 
hence the term polyconic. The Geological Survey sheets 
are made on this system. There is a straight central line 
representing the central meridian of the sheet. The four 
boundaries of the sheet are parallels of latitude or meridians 
of longitude. They appear to be straight lines also, but 
they are not. By careful measurement, one will find that 
the northern boundary is a little shorter than the south- 
ern boundary. Likewise, one will find that all four boun- 
daries are slightly curved. 

14. The U. S. Geological Survey sheets are polyconic 
and generally 1:62,500 (about 1"=1 mile) and 1:125,000 
(about i"==l mile). The 1:62,500 sheets cover 15' of lati- 
tude and 15' of longitude. 



MAPPING LARGE AREAS 113 

15. Grid System in the United States: — The sys- 
tem of map co-ordinates used by the U. S. Army is based 
on 1000-yard squares or grids. The whole of the United 
States is divided into seven zones, each 8 degrees of longi- 
tude in width, but with an additional h degree at each side 
for overlap on the adjacent zone. The following table shows 
the designation of the several zones across the United 
States, with their central meridians and the meridians which 
limit the zones : 



Designation 


Central meridian 


Limiting meridians 


A 


73° 


68° 30'— 77° 30' 


B 


81° 


76° 30'— 85° 30' 


C 


89° 


84° 30'— 93° 30' 


D 


97° 


92° 30'— 101° 30' 


E 


106° 


100° 30'— 109° 30' 


V 


113° 


108° 30'— 117° 30' 


G 


121° 


116° 30'— 125° 30' 



The only exception, so far as limiting meridians are 
concerned, is the strip over Maine to the eastward of longi- 
tude 68° 30' which is included in the grid tables for zone 
A, though it is more than 4° 30' to the eastward of the cen- 
tral meridian of the zone. 

An origin of co-ordinates for each zone is arbitrarily 
selected southwest of the area covered by the zone, so that 
the co-ordinates for all points will be positive. The point 
selected as the arbitrary origin is 1,000,000 yards west 
and 2,000,000 yards south of the intersection of the central 
meridian of each zone with the parallel 44° 30' of latitude. 
The vertical co-ordinates run from about 600,000 yards at 
the west boundary of each zone to 1,400,000 yards at the 
east boundary, the 1,000,000 co-ordinate line co-inciding 
with the central meridian. 

The horizontal (Y) co-ordinates run from about 500,000 
at 28° N. latitude to 3,000,000 at about 49° N. latitude. 

Points on the overlaps between zones will have a dif- 
ferent set of co-ordinates for each zone. The two grid sys- 
tems may be placed in different colors on maps of the over- 
lapping areas. 

16. Grid Azimuths: — Owing to the converging of 
meridians, any line on the earth's surface (except at the 
central meridian of the zone) will make a different angle 



114 TOPOGRAPHY 

with the grid meridian from the angle it makes with the 
geographic meridian. At points west of the central meri- 
dians, the grid azimuths are greater than geodetic or true 
azimuths; at points east of the central meridians they are 
less. The differences vary from zero at the central meridian 
to about 3i degrees at the eastern or western edges of the 
respective zones. 

further details regarding the above system may be 
found in Special Publication No. 59, U. S. Coast and Geodetic 
Survey, "Grid System for Progressive Maps in the United 
States." 

17. System of Mapping Large Areas: — A complete 
system of mapping large areas consists of: 

(a) Preparation of skeleton projection sheets, involv- 
ing two steps : 

1. Securing of data. 

2. Production of skeleton projection sheets. 

(b) Field work, involving three steps: 

1. General control. 

2. Local or transit traverse control. 

3. Sketching in. 

(c) Making final sheets, involving two steps: 

1. Drafting of final maps by transfer from field sheets. 

2. Printing or reproduction of maps. 

18. The securing of data consists in finding all possible 
available information. There is practically no large area 
in the world in which maps have not been made of at least 
some small portions. There are generally railroad surveys 
which can be used. Often, astronomers have worked out 
accurately certain local points, all of which can be obtained 
for use in mapping the area. 

19. The production of field sheets consists simply in 
(a) deciding on the size of the field sheet; (b) putting on 
it all of the available accurate data; (c) putting on it also 
all of the control data secured by our own mappers; (d) 
furnishing as a memorandum all of the data which may be 
useful but is not known to be accurate. 

20. If a country has never been mapped at all, it is nec- 
essary to secure control, for the control of a map is like 



MAPPING LARGE AREAS 115 

the steel framework for a modern skyscraper. By control, 
is meant the accurate location of certain points, say 100 
miles apart for primary control and 10 miles apart for sec- 
ondary control. This has been done in the past by expand- 
ing triangulation from a base line measured to the highest 
attainable accuracy, and using the most refined instruments 
of precision in measuring the angles. An area of large ex- 
tent is covered by two sets of triangles, primary, with sides 
up to 30 miles long, and secondary with sides up to 10 miles 
long. 

21. Control within the triangulation and tied thereto 
or for small areas not covered by triangulation is often es- 
tablished by traverse lines. These lines may be run with 
a high degree of accuracy, and with fair speed, and with a 
number of parties in the field, cover considerable area. Such 
method of control is what may be expected in military sur- 
veys. 

22. For hundreds of years, it has been possible to find 
by astronomy quite accurately the latitude of a place, but 
not the longitude. Lately, however, the telegraph, and still 
more lately, the wireless, are being used until it is now pos- 
sible for a survey party equipped with a theodolite, a wire- 
less receiving outfit, and an ephemeris (astronomical tables) 
to locate itself in the middle of a desert or mountainous 
country a thousand miles away from any other human be- 
ing. The finding of the longitude of a point consists in find- 
ing the exact time when a star or the sun passes the meri- 
dian of the place; and then finding by calculation, using the 
ephemeris, the difference between this time and the time 
the star or sun passes the meridian of Greenwich. A clock 
is set with say Greenwich time and taken out into the field ; 
the time is observed by this clock when the star or sun 
passes the meridian of the place ; the difference, with cal- 
culated corrections, gives the longitude. It all depends on 
the clock, which has errors which are very small but vary 
from day to day. The daily error is so small that it can be 
assumed proportionate and calculated and compensated for ; 
the error for several days cannot be assumed as propor- 
tionate and cannot be so calculated, consequently the cal- 
culated longitude is not exactly correct. Lately, wireless 



116 TOPOGRAPHY 

helps a great deal, because the clock error can be determined 
each day ; and we need only consider the daily error, which 
as stated above is assumed as proportionate to the whole 
day and is so small that the result is quite accurate. In run- 
ning the Mexican boundary lines, a clock was used and was 
fairly satisfactory; but the clock gradually accumulated 
varying errors while being packed around over the rough 
country ; and when the party arrived at a telegraph station, 
they had to refigure all their observations in order to adjust 
for the errors of the clock, and even then they had to as- 
sume that the errors were proportionate to the time since 
the clock error was last determined. 

23. Having acquired primary control, it is then neces- 
sary to run a series of secondary triangles called "secondary 
triangulation," in order to provide a second set of known 
points closer together and more convenient for detailed 
use. If the country is difficult and the map need not be 
exceedingly accurate, this second set of known points may 
be determined in latitude and latitude astronomically, or, 
if conditions warrant, by traverse. This second set of 
known points should not be more than 10 miles apart and 
preferably less than that. 

24. Before the sketcher starts to work on an area, he 
must have points closer together even than 10 miles, be- 
cause with sketching instruments, it is not possible to make 
a series of sketches covering an area 10 miles square which 
will be accurate enough. Consequently, a series of traverse 
lines is run connecting these points of the secondary trian- 
gulation. Branch traverse lines may be run so as to give 
as close a net of control as the circumstances demand. 

25. By these means, we secure a control net or frame- 
work on which may be hung in their proper relation the de- 
tails determined by the methods of sketching. 

26. In the general system of control, transit traverse, 
and sketching, as noted above, it is necessary to adjust the 
triangles and transit lines. The curvature of the earth 
makes this necessary, and in addition there are always cer- 
tain errors in closing a triangle. The sum total of the de- 
grees of a measured triangle will never be exactly 180 de- 
grees. In such case, the difference is not applied to the last 



MAPPING LARGE AREAS 117 

angle determined; but the total difference is divided out 
among all the angles of the triangles, or series of polygons. 
Similarly, if the lines are not the proper length, the adjust- 
ment is made on all of the lines and not simply on the last 
line. 

27. All of the control points having been plotted on the 
field sheet as previously stated, the transit and sketching 
parties are assigned certain sections for work. In the as- 
signment of areas for sketching parties it is advisable to 
make the division with some regard to the roads and trails 
that give accessibility to the areas rather than by an arbi- 
trarily adopted set of dividing lines. 

28. The sheets furnished the field parties should be of 
uniform size adapted to the equipment, sketching board, 
plane table, etc., that is to be used. These sheets should 
have upon them the control, and all other data that can be 
reliably placed on them at the office issuing them. Any 
other data on hand which might be of use to field parties 
should be issued to them; 

29. A central party controls transit and sketching 
parties. It is assigned its area, given its field sheets, and 
sent out into the field. The transit parties run their transit 
traverses ; central party checks and plots their work and 
turns over the field sheets to the sketching parties. These 
fill in the areas, then the central party checks and co- 
ordinates the field sheets and sends them to the main office 
for final check before being turned over to the printing 
and reproducing outfit. 

30. The two steps in making final sheets are the trans- 
fer of field data with good drafting and then the printing 
of the maps. Each field sheet must fit with its adjacent 
sheet. The work of adjusting the field sheets of adjacent 
field parties is done in the central office with the assistance 
of representatives of the field parties where necessary. Ad- 
jacent sheets from one field party should require no adjust- 
ment for concordance by the central office. The central 
office has much preliminary work to do when topography 
is taken from airplane photographs. 

31. The transfer force has much special work when we 
use aeroplane photographs. Also, the transit work of the 



118 TOPOGRAPHY 

field parties must always be checked. Altogether, the- 
transfer force has much to do even before it begins the 
drafting. 

32. The printing of the maps is an art in itself. It 
requires special equipment and special men. In France, the 
29th Engineers did this work. They were very specially 
selected men, and they did the work so well that most peo- 
ple thought it was easy to do. 

System for the United States Army 

33. In case the Army of the United States should oc- 
cupy a new country which has been unmapped, it would 
be advisable to promptly commence making maps of the 
country. The system followed should be as stated above; 
if such a system is not followed, there are always unneces- 
sary difficulties. This system was followed in Hawaii and 
in the Philippines, and it worked out very well. However, 
in Cuba we used a very different system. It appeared that 
for certain reasons is was necessary to begin the field work 
of sketching without delay. Consequently the sketchers 
were hurried out into the field before control had been ob- 
tained of the country. As a result, the. sketching parties 
made sketches which, in some cases, could not even be ad- 
justed by expert draftsmen in accordance with the actual 
distances as developed later, when the primary and secon- 
dary control were obtained. In most cases it was possible 
to adjust these sketches, but where this could not be done, 
it was necessary to have a sketching party go all over the 
work again. 

34. In map work by the army it is best to follow the 
approved system and apply the available agencies to the 
accurate work. Consider each of the steps of the approved 
system, and see how to apply it to the army. 

35. Securing of Data: — This would be done by the 
engineers on the staff of the general headquarters and at 
other headquarters. Most of the data is obtained from 
books or from records in the capital city of the country. In 
Cuba, practically all of the data was secured in Havana ; in 
one case, railway data was secured from the headquarters 
in the United States of this particular railway. 



MAPPING LARGE AREAS 119 

36. Production of Field Sheets: — This will be done 
by the reproducing company of the topographical engineer 
battalion. It might be done at one central headquarters 
by all of these companies working together, or each battalion 
might work at some central point in its own district. 

37. Control: — This work would require expert map- 
pers. For this purpose, the survey company of the topo- 
graphical engineers would be used and they should start 
at once. These men securing primary control would also 
be the ones to secure secondary control. It is estimated 
roughly that one party could secure primary and secondary 
control for an area of about 10 miles square in one month. 
Assuming each engineer survey company furnishes 10 con- 
trol parties, it should be able to get 10 points per day, or 
100 points in 10 days. Allowing for errors and other delays, 
and assuming these control points 8 to 11 miles apart, this 
engineer survey company should easily secure control on 
an area 100 miles square at the rate of one area per month, 
after the work had well started. 

38. Transit Traverses and Sketching: — One would 
naturally expect that engineer troops would be used for 
running the transit traverses and for rilling in by sketching, 
but there are not enough engineers and never will be enough 
to do all the map work of mapping a large area. Calculations 
in the office of the Chief of Engineers show that a survey 
company can map completely and alone about 5,400 square 
miles per year. As a survey battalion would need 1 company 
for reproduction, they could put only 2 companies in the 
field. As a result, a survey engineer battalion could map 
10,800 square miles per year. There were in the proposed 
Army Reorganization Bill 2 topographical battalions listed, 
each battalion having 2 companies for survey work and 1 
company for printing and reproduction work. 

39. For the bulk of this work, the army would have 
to organize and train special transit and sketching parties. 
It would use say a survey company and the mapping de- 
tachments of the division engineer regiments and obtain 
the remaining personnel by details from the infantry, cav- 
alry, and artillery. Two months' training would be desir- 
able before sending one of these parties into the field. The 



120 TOPOGRAPHY 

division engineer regiments should be able to furnish a 
limited number of trained topographers. The best use of 
such men would in general be to give them pivotal positions 
in newly formed parties. 

40. In Cuba, they did not train any special parties ; and 
results were not very satisfactory. In the Philippines, they 
gave a two months' training to these special parties before 
sending them out into the field and the results were quite 
satisfactory. Incidentally, no time is lost by such training, 
as the control parties should be given about 2 months' start 
in order to secure control for field sheets for use of these 
specially trained parties. 

41. The size of the special parties would vary accord- 
ing to the kind of country and the degree of friendliness of 
the inhabitants. In Cuba, it was found that a sketcher 
could do best if he were accompanied by three men. One 
man would assist him by holding his horse, or counting, or 
putting down data, and the other two were the cook and 
packer. One of these parties would go out to a certain 
section and map all of that section before returning. Occas- 
ionally the packer would appear at his headquarters with 
his pack mule and take back more rations. Several sketch- 
ing parties could thus travel through a certain section of 
the country, the central party moving along a road or trail, 
and the others scattering out into their assigned areas, 
remaining by themselves until the area had been mapped 
and then returning to the central party. 

42. Assume that each sketcher can sketch one square 
mile each day, and that each transit man can traverse 5 
miles each day. In a 100-mile square there are 10,000 square 
miles to be sketched and 20,000 linear miles to be traversed. 
This is equal to 4,000 traverse party days and 10,000 sketch 
party days. This shows that 4 traverse parties and 10 
sketching parties could finish the 180-mile square in 1,000 
work days (about 40 months including delays, etc.). If the 
work must be finished in 4 months, it would mean 40 trav- 
erse parties and 100 sketching parties. 

43. For different countries, the various parties will be 
different. However, as a fair basis, assume that the coun- 
try is about 20 per cent wooded, and that the inhabitants are 
hostile but have no organized bands and act only as in- 



MAPPING LARGE AREAS 



121 



dividual enemies, 
the following: 



The various parties could then consist of 



(a) Control party: 



(c) Traverse party 



1 officer or sergeant. 


1 officer. 


2 instrument men. 


1 cook. 


1 recorder and calculator. 


1 packer. 


2 medical men. 


1 medical man. 


1 draftsman. 


3 guards. 


4 woodsmen. 


4 instrument men 


1 cook. 


•7 woodsmen. 


1 assistant cook. 


2 pack mules. 


4 guards. 




2 teamsters. 




2 Signal Corps men. 




8 mules. 




2 wagons. 




1 wireless receiving outfit. 




Total, 3 officers and 28 men. 




(c) Central party: 


(d) Sketching 


2 officers. 


1 cook. 


1 medical officer. 


1 packer. 


2 draftsmen. 


1 medical man. 


1 cook. 


3 guards. 


6 guards. 


2 sketchers. 


2 extra medical men. 


2 pack mules. 



15 extras. 
2 wagons. 
8 mules. 
Total, 3 officers and 28 men. 

The above estimates of personnel are reasonable. They 
are not exactly the same as were used in the Philippines, 
but that country was not hostile and natives were used as 
cooks and cargadores. 

44. The engineer topographical battalion would prob- 
ably be a basis for any complete map organization. , By 
using the preceding figures, and assuming that the con- 
trol parties are about two months ahead and everything is 
working smoothly, the following appears to be a well bal- 
anced organization: 

1 topographical battalion headquarters. 
1 printing and reproducing company. 
1 survey company (10 control parties). 
40 mapping parties as follows (including 1 survey company 

and all division engineers available). 
40 central headquarters parties. 
160 traverse parties. 
400 sketching parties. 



122 TOPOGRAPHY 

This organization could map one 100-mile square or 
10,000 square miles in one month. 

45. The following tables show more clearly the com- 
plete and balanced mapping organizations which can map 
10,000 square miles per month. Such an organization would 
be assigned a district. An examination of this table shows 
the very large force required to produce good maps of en- 
tirely unmapped country in a short space of time. The con- 
ditions would be very exceptional which would permit the 
use of so much force for the purpose either in campaign or 
at any other time. 

46. Cost: — At present the cost of topographical map- 
ping to the field scale 1:48,000 or 1:62,500 ranges from $25 
to $50 per square mile, the average countries costing about 
$33 per square mile. These figures increase rapidly with in- 
crease of scale, and 1:10,000 scales run into hundreds of 
dollars per square mile. A survey of the Island of Guam in 
1915 at 3" to the mile for 210 square miles and 6" to the 
mile for 30 square miles cost close to $40,000, which is $167 
per square mile. 

Assistance by Aeroplanes 

47. The development of aero-photography indicates 
that it will have a marked influence on topographic mapping 
in the speed of work and in the accuracy and amount of the 
detail shown. 

(a) The average work to date by one aeroplane 
is about 35 square miles in 2h hours, which would probably 
constitute an average day's work if we count in the break- 
downs and flying to and from the flying field. In other 
words, an aeroplane with a well trained mapper can probably 
do thirty times as rapid work as one sketching party. 

(b) An aeroplane party should consist of the following l 

1 Officer to lay out the photograph work and supervise. 

1 pilot. 

1 mapper (photographer). 

3 mechanics. 

5 field men. 

3 control men. 

There should be an office party of not less than — 

1 man in charge. 

3 men on transformer. 

3 men preparing transformer photographs. 

6 draftsmen. 



MAPPING LARGE AREAS 



123 




124 TOPOGRAPHY 

(c) Aeroplane photographs are of no real value in 
determining elevations. By taking photographs at an angle, 
this is possible ; but to date no very practicable method has 
been devised. 

(d) Thus, although it is known that aeroplane photo- 
graphy has a great many possibilities, and although it is cer- 
tain that it will be used to assist in any mapping of large 
areas by the United States Army, it appears that it has also 
very many difficulties. It can surely be used to assist in 
sections where contours are not required; it can be most 
profitably used for filling in details and for correcting de- 
tails where the country has been poorly or incompletely 
mapped; it can be used for rapid work in correcting maps 
already in existence; it cannot be used for accurate work 
unless primary and secondary control have been obtained, 
but it can be used to obtain an inaccurate but effective map 
covering a large area, even without control. The great ad- 
vantage of the aeroplane is its speed; and the determining 
factors of the speed of making the map is probably not the 
actual time of photographing the area, but the kind of 
camera, the distance from the ground, the number of ex- 
perts available for reading and transferring the aeroplane 
data to a real map, and the number of experts available 
for reproducing the map. 

48. Engineer troops will generally assist in mapping 
large areas. Contrary to the general belief, not many of 
the division engineer troops are experts in making maps. 
Each division regiment has a topographical section, but its 
number is very limited. All of the officers of the regiment 
should be excellent map makers; but very few of the sol- 
diers have the necessary experience. In addition, it must 
be remembered that the engineer troops have other duties 
to perform; and in some cases even the topographical sec- 
tions are not available for mapping the area, as they are 
needed for sketching and survey work connected with the 
work of their regiments, such as roads, buildings, etc. The 
main reliance for mapping large areas will be the topograph- 
ical engineers, assisted by specially trained parties from 
other sources. 



CHAPTER VII 

Map Reproduction 



1. General Classification of Methods of Repro- 
duction: — The various methods of reproduction are di- 
vided into four classes, according to the principle underly- 
ing the method, viz.: 

(a) Where the copy to be reproduced is obtained on a 
transparent sheet, with the drawing in opaque lines, and the 
reproduction is done by printing from this transparent sheet 
on sensitized paper by means of light. The methods of repro- 
duction using this principle are blue printing, brown printing 
and photography. 

(b) Where the copy is reproduced with special ink on paper 
and this ink is transferred to another substance from which 
copies can be made by pressing blank pieces of paper on it. This 
is the principle upon which the hectograph is based as well 
as the forms of hectograph called by other names, such as the 
jelly roll and duplicator. 

(c) Where paper or cloth is so cut or treated that ink can be 
rubbed or forced through it onto blank sheets below. This is the 
principle upon which the mimeograph, neo-cyclostyle (used in 
France), and the Ellam duplicator (used by the British army) 
are based. 

(d) Where copy is transferred, generally by a rather com- 
plicated process involving several transfers, to another substance 
which is so fixed that the impression of the copy can be inked 
and so that when paper is pressed in contact with the substance 
a reproduction of the original will be made. This principle is 
the one used in the Dorel and lithographic methods of repro- 
duction. 

2. Drafting is generally the slowest part of any work 
of reproduction. The classification below is based on the 
drafting required. 

First: Methods which require the redrafting of the 
map or sketch on transparent paper or cloth : 

(a) Blue and brown prints. 

(b) Dorel. 

(c) Certain processes in lithography. 

Second : Methods which require a redrafting of the 
map or sketch on special poper or with special inks : 

(a) Hectograph, jelly roll, duplicator. 

(b) Ellam duplicator. 

125 



126 TOPOGRAPHY 

(c) Neo-cyclostyle. 

(d) Mimeograph. 

(e) Autographic process in lithography. 

Third: Methods which do not require redrafting: 

(a) Special cases in blue printing. 

(b) Photography. 

(c) Photographic process in lithography. 

Of the above named methods the hectograph is the 
only one which will reproduce a number of colors at once. 
The others all require a special reproduction for each color. 

3. Description of Methods of Reproduction: — A 
short general description is given below of the most common 
methods of reproduction. 

Hue Prints 

4. The procedure followed consists in placing a piece 
of prepared paper, and the tracing it is desired to repro- 
duce, in a frame with one glass side. The glass holds the 
transparent paper in contact with sensitized paper. Then 
the frame is placed in sunlight or in strong artificial light 
for a certain period of time, depending upon the intensity 
of the light, the transparency of the paper, and the. sen- 
sitiveness of the prepared paper. After this exposure the 
print paper is washed out in water and when dried, the print 
is ready for use. 

5. The equipment for blue printing is simple, con- 
sisting of the proper kinds of paper, a frame, a dark room, 
and facilities for washing and drying paper. For relia- 
bility, artificial light is also necessary. Two men should 
be available for this work. To make and dry one blue print 
requires from 30 minutes to 3 hours, depending upon con- 
ditions. The speed is limited by the capacity of the frame. 
As a general rule if more than 20 copies are desired it is 
better to use some' other method. 

The result obtained consists of white lines on a blue 
background. A blue print can be corrected or changed as 
desired by drawing on it with a solution which fades out 
the blue and makes white. 

This brings up another point of interest. Ink lines can 
be drawn on a blue print and then the color faded out leav- 



MAP REPRODUCTION 127 

ing the black lines on a white background. This resulting 
drawing can be photographed and reproduced. The applica- 
tion of this scheme is quite varied. For instance, many of the 
plates in the Engineer Field Manual were made by photo- 
graphing the object, say a pack mule, making a blue print 
from the negative, inking the important features of the blue 
print, fading out the blue, and then reproducing the result- 
ing drawing. It gives a very clear plate with nothing on 
it except essential details. 

6. Ordinary paper is sufficiently translucent to permit 
a blue print to be made through it. It is a very slow process, 
however, as the time of exposure depends upon the trans- 
parency of the paper. A map can be reproduced in this 
way. The result is readable and in case a few copies only 
are desired it is a very quick way of getting them. The 
result is, of course, in one color. If the original map can 
be oiled it will increase its translucency and copies can be 
made much more quickly as the time of exposure is reduced. 

As an example of this, before the St. Mihiel operation, 
G3, G.H.Q., got out a number of maps showing the visible 
areas from various observation posts within the German 
lines. The data for these maps were obtained by the use 
of relief maps and the shadow effect from small electric 
lights. The reproduction facilities at this time were too 
busy to do the work, and it was not possible to have these 
maps reproduced in ordinary ways. It was necessary to 
devise some scheme, so an original map was made and oiled 
to make it transparent. With it about fifty copies were re- 
produced rather quickly by ordinary blue printing methods. 

Road sketches are often reproduced in this same way. 
If the sketches are good, they are taken in the evening after 
the day's work, joined up and finished in ink. The whole 
map is oiled and reproduced by blue printing. This permits 
a readable map to be obtained in a very brief time. 

Brown Prints 

7. The process of making brown prints is very similar 
to that of making blue prints. The equipment is almost the 
same. In the case of the brown print, the exposure is a little 
shortened, and after exposure it is necessary to wash the 



128 TOPOGRAPHY 

print, put it in a fixing solution, and then wash it again for 
about half an hour. It, therefore, takes a little longer to 
make a brown print than it does to make a blue print. 

A brown print gives a result of white lines on a brown 
background. This brown color is impervious to light, so 
brown prints are largely used as negatives. Printing 
from a brown print onto brown print or blue print paper 
gives a result of brown or blue print lines on a white back- 
ground. These last named prints are valuable in case it is 
desired to have a result which can be written on with black 
lines. A number of negatives can be made and then the print- 
ing will proceed more rapidly, using several negatives so 
as to make several prints at once. If more than 20 copies 
are desired other methods are generally faster. 

Neo-Cyclostyle 

8. This method of reproduction was in general use 
throughout the French army during the war. 

The drawing to be reproduced is pasted lightly on the 
base plate. The wax paper fitted in the frame is then 
placed over the drawing. The drawing is traced on the wax 
paper with an instrument which has a very fine tooth wheel, 
making a fine perforated line on the wax paper. The wax 
tracing is then removed, a plain sheet of white paper sub- 
stituted for the original drawing, and the wax tracing 
placed over it. Ink of the desired color is then rolled over 
the wax paper and printed on the plain sheet through the 
perforated line. 

About sixty reproductions can be made per hour and 
from one to two hundred copies can be made before 
the wax paper tears and a new tracing is necessary. More 
than two hundred copies can be made by the use of silk 
gauze stretched on a frame which is placed over the wax 
paper. The inking is done over the silk gauze and this 
keeps the wax paper from tearing. 

With the exception of the paper used, the entire equip- 
ment can be carried in a box 2' x 2' x 9". For small jobs, 
two men can make the best speed. On special jobs, three 
men can often be advantageously used. 



MAP REPRODUCTION 129 

One advantage of the method is that registering can 
be accurately done. When matter is printed on a map it is 
essential that it be put in the proper place with respect to 
the topographic features on the map, that is, that it reg- 
isters properly. To accomplish this, the tracing is so ar- 
ranged that two points marked on it near the edge corres- 
pond to two points which appear on the map upon which 
the printing is being done. When the over-print is made, 
the points on the tracing are placed exactly over the points 
on the map and this insures that the over-print has the 
proper position to be correct for all features on the map. 
The neo-cyclostyle was largely used by the French corps 
to make minor changes in their Plans Directeurs, changes 
such as those as resulting from aeroplane photographs, 
raids, etc. 

The advantages of this method are simplicity, speed 
and reliability. The disadvantages are that the size of the 
reproduction is limited and but one color at a time can be 
printed. 

Ellam Duplicator 

9. This reproduction equipment was largely used by 
the British. In using this equipment, the drawing to be 
reproduced is placed on the base and a frame containing 
fine silk gauze is stretched over the drawing, and on top of 
this another frame containing wax paper. The drawing is 
then traced on the wax paper with an ordinary stylus and 
the silk screen produces a corrugated line. The method of 
printing is the same as that for the neo-cyclostyle. The 
number of copies which can be made and the advantages 
and disadvantages of this method also correspond to those 
of the neo-cyclostyle. 

Hectograph 

10. In this method of reproduction, a drawing or trac- 
ing is made with special inks and is pressed on the hecto- 
graph tray, which is filled with a base composed of gelatin, 
clay, and glycerine. When the paper is pulled off the draw- 
ing appears reversed on the gelatin surface. A piece of 
blank paper pressed on the surface and then withdrawn 
shows the drawing printed on it. When through, the draw- 



130 TOPOGRAPHY 

ing can be erased off the base and another drawing repro- 
duced. 

From twenty to forty copies can be made in one hour* 
It takes about fifty per cent more time to make a tracing 
with the special inks necessary than it does to make a 
tracing with ordinary inks. For best results, two or more 
hours are necessary for the ink to dry on the drawing be- 
fore it is transferred to the gelatin surface. From twenty 
to forty copies can be made from one impression. 

The equipment is fairly heavy and weighs more than a 
hundred pounds. Several trays of the composition are gen- 
erally necessary and from two to three men are required for 
the reproduction work. 

The main advantages of this method are simplicity, 
rapidity, and reproduction of colors. The disadvantages 
are that the 'number of copies is limited, the equipment is 
quite heavy; the result is not a finished reproduction and 
the paper after being in contact with the gelatin surface 
retains a film of the compound on it and is sometimes sticky. 

There are several other forms of hectograph. The 
French used a gelatin coated paper roll- instead of the clay 
composition base. This was generally known in our army 
as a jelly roll. The method of using this roll was the same 
as that of using the hectograph. As many as twenty-five 
fair prints could be made. The ink could not be washed 
off the roll, but after several days it would diffuse into 
the mixture and the roll would be ready for use again. 
There are many kinds of commercial hectographs on the 
market. 

Dorel Process 

11. This method of reproduction was largely used by 
all allied armies in Europe. A melted gelatin mixture is 
poured on a zinc plate and allowed to cool for a brief per- 
iod. A blue print of the tracing to be reproduced is made, 
but not developed, and is placed face down on the gelatin 
coated plate and smoothed out in contact with the gelatin. 
Upon removing the blue print the lines will be found faintly 
transferred to the gelatin. These lines will take ink from 
the ink roller and the gelatin surface will not. After roll- 



MAP REPRODUCTION 131 

ing the gelatin with the desired color of ink, a print can 
be made by smoothing a sheet of paper over it. 

Using this method, it takes at least one hour to get 
twenty prints. From twenty to forty prints can be made 
for each blue print. After twenty to forty prints are made 
a new blue print and gelatin plate must be used. 

The equipment necessary is fairly complicated, as blue 
print facilities must be available as well as arrangements 
for heating and drying the gelatin. Zinc plates, ink, ink 
rolls, etc., are also necessary. Three men are required to 
operate the equipment efficiently. 

The result obtained is very good; and most reproduc- 
tion work in France, when less than two hundred copies 
were desired, was done by the Dorel process. An example 
of this work is the order of battle maps issued at G. H. Q. 
It is a very quick method of reproduction, considering the 
appearance of the results. The disadvantages of the method 
are that the gelatin mixture is a secret preparation and is 
sometimes unreliable, especially in very cold or very hot 
weather. A separate tracing and blue print are necessary 
for each color and fifteen to forty prints can be made with 
one plate. 

Assuming twenty prints for a blue print, it is more 
economical to print from zinc plates when more than two 
hundred copies are desired. 

Lithography 

12. The finest reproduction work is done by litho- 
graphy. The word literally means "to write on or from 
stone." The first lithographic work was done on stone, and 
even yet some of the finest work is done in this way. Zinc 
plates, however, are now generally used. There are a num- 
ber of lithographic methods in use. 

Practically all standard maps are made by lithography. 
Examples of lithography can be seen in almost any book or 
newspaper, as most reproduction work of pictures, charts, 
drawings, etc., in quantity, is done by lithography. 

The equipment varies from small hand presses, such 
as those used in engineer regiments, capable of printing 



132 TOPOGRAPHY 

forty copies per hour, to the large rotary offset presses 
capable of running as many as five thousand copies per hour. 

There are two general methods in use in commercial 
work. In one, drawing is done direct upon the plate; and 
in the other, the drawing is transferred to the plate by one 
of a number of different processes. 

The zinc plates used in this work have to be carefully 
prepared. They are put through a process called "graining." 
By graining is meant that the surface is made slightly 
rougher so as to absorb or retain the lines. This graining 
is done by the use of powdered pumice stone, water, and 
spinning glass marbles on the surface of the plate. After a 
plate is used once, regraining is necessary. 

In army lithographic work, no drawing is ever done 
directly upon the zinc plate. It is always transferred to the 
plate and our methods of lithographic reproduction are 
classified according to the way in which the zinc plates are 
prepared. Using this classification, the methods most gen- 
erally used in lithography are the Mowing : 

(a) Autographic process. 

(b) The direct process. 

(c) The photographic process. 

(d) The transfer process. 

These methods will be briefly outlined. 

(a) Autographic Process: — In this process the orig- 
inal drawing or a tracing of it is made with special ink 
upon certain prepared paper of a transparent nature. The 
prepared paper is then placed between moist blotters until 
it is damp. The moist tracing is then placed upon a pre- 
pared plate. This plate is run through a press a number of 
times and moistened until the transfer ink has been pressed 
from the paper to the plate. The plate is then thoroughly 
washed with water and covered with a solution. It is then 
rubbed with another solution which prevents the ink from 
adhering to any place on the plate with the exception of the 
impression left by the transfer. After this the plate is 
rubbed with ink, dried, the solution washed off and a fresh 
one applied. The plate is then washed with turpentine 
which removes the ink lines, leaving a white impression 
on the plate where they have been. The plate is again 
washed with another solution, dried and then washed with 



MAP REPRODUCTION 133 

water. It is then gone over with a dampening cloth and 
rolled up with printing ink. It is kept moist during this 
rolling to prevent adherence of ink upon other parts of the 
plate than the design. The theory of this last is that water 
will not adhere to the lines, which are greasy, and the greasy 
ink will not adhere to the water which is on the rest of the 
plate. 

If only twenty-five or thirty copies are desired, it will 
not be necessary to etch the plate. When more than thirty 
copies are desired, the plate is etched with chemicals. 

The above outline has been given mainly to give an 
idea concerning the large number of separate operations 
and the complication involved in reproduction by litho- 
graphy. 

(b) The Direct Process: — A tracing on transparent 
paper or cloth is made with opaque drawing ink, the zinc 
plate is coated with a solution sensitive to light, and the 
plate and tracing are then put in a frame as in blue printing 
and exposed to sunlight or a strong artificial light. The 
plate is then finished up in a manner similar to that de- 
scribed in the process outlined above. 

(c) Photographic Process: — In this process the 
drawing is photographed on a glass plate, from which 
plate a zinc plate is prepared by essentially the same meth- 
ods as in the direct process just described. 

(d) Transfer Process: — New plates may be made 
from old ones by a transfer involving the use of special 
transfer paper and ink. It is by this method that new plates 
are made by combining portions of several plates. 

The autographic and direct processes do not involve 
the use of a camera or of complicated methods, hence they 
are adapted to the field or small plants, such as that of the 
corps topographic section. The photographic and trans- 
fer process involve rather complicated methods and very 
careful work. The photographic process also requires a 
reproduction camera. Hence the last two processes are 
only adapted to large plants such as a base printing plant 
or that at army headquarters. 

It is to be noted that both the autographic and direct 
processes require a tracing. The autographic is not as re- 



134 



TOPOGRAPHY 



liable as the others, because if something goes wrong with 
the plate the whole drawing must be made over again. It 
has the advantages that it is entirely independent of light, 
it is more rapid than the direct process, and the results 
with trained men are satisfactory. The photographic pro- 
cess does not require a tracing and permits of enlargement 
or reduction of the original drawing as may be desired. 
The direct process was used in most large plants during 
the war, especially those at Washington. Its main advan- 
tages are great speed and certainty in its results. 

13. The following table gives the approximate speed 
and capacities of various reproduction methods described : 



Apparatus 


1 copy 
5 min. 


20 copies 


200 copies 


1000 copies 


Blueprint* 


1 hr., 40 min. 










Duplicator** 


2 hrs. 


2 hrs., 30 min. 










Cyclostyle 


3 hrs. 

4 hrs. 


3 hrs., 10 min. 


5 hrs., 10 min. 






Hand lithograph 


5 hrs. 


14 hrs. 


54 hrs. 


Power Lithograph 


4 hrs. 


4 hrs., 5 min. 


4 hrs., 20 min. 


5 hrs., 20 min. 



*Good sunlight. 

**Same time for multi-colored job. 

14. Facilities for Reproduction Available in the 
Various Units. 

It is reasonable to assume that in our future operations 
the reproduction facilities available to each unit will be 
the same or similar to those used in France during the late 
war. There the authorized equipment was as follows : 

Division — Neo-cyclostyle or Ellam duplicator, and hectograph. 

Corps — A hand lithograph press capable of printing sheets 
26"x36"; a Dorel equipment; and the equipment noted 
for a division. 

Army — In addition to the above equipment given for a corps, 
a rotary lithographic press capable of printing sheets 
35"x 45", and type presses. 

Base plant — In addition to the above equipment given for 
an army, rotary lithographic presses capable of print- 
ing sheets 35"x 45", and type presses. 

15. The above equipment belonged to G2. In each 
sapper engineer regiment there were lithograph, Dorel and 
blue print equipments. The lithographic equipment was 



MAP REPRODUCTION 135 

a very small one. The maximum size of reproduction was 
24"x30". 

Mobile Train 

16. With the American Forces in France, in 1918, there 
was provided a printing train designed for the work required 
by an army. The whole equipment was mounted on trucks 
both for transportation and operation. Power for opera- 
tion was furnished from a dynamo coupled to the motor of 
one of the trucks. The equipment consisted of a complete 
outfit for drafting, photography, map reproduction and 
printing. 

The idea of mobilizing a printing train in this manner 
has not been finally adopted, nor has standard equipment 
been provided. There are some serious objections to 
mounting the heavy and delicate machines on trucks in 
operating positions, and it appears feasible only where good 
roads exist. 

A. E. F. Results 

17. 1st Army Plant. Nine officers and 90 men. In 10 
weeks distributed over a million and a quarter maps and 
documents — of these 550,000, involving 800,000 impressions, 
were printed at the army plant. 

2d Army Plant. Sixteen officers and 155 men. In 5 
weeks distributed 540,000 maps and documents. Of these 
over 500,000, involving 000,000 impressions, were made at 
the army plant. 

18. Map reproduction plants will give satisfaction in pro- 
portion as the following points are appreciated by all con- 
cerned : 

(a) A realization o fthe importance of an adequate 
supply of maps to the conduct of military operations. 

(b) Advance information of the demands that are to 
be made for maps. The authorities charged with map re- 
production must at all times be kept properly informed as 
to the prospective needs with respect to maps. No one 
needs this advance information more than they do. Defi- 
nite information is not essential, but they do need to be 
told concerning what the future demands on them will be. 
If they do not have this advance information the conduct 
of the operation will be severely hampered by lack of maps. 



136 TOPOGRAPHY 

(c) Keep the colors on the map and the drawing to 
be reproduced down to a minimum. 

(d) State the time the work is desired. 

(e) If practicable state the method of reproduction that 
will be satisfactory. 

. (f ) If possible, state whether any future demands for 
the same work will be necessary. 

(g) Present work to be reproduced in the form of trac- 
ings when practicable. If draftsmen are available the re- 
production of any job can often be facilitated by having 
them make the necessary tracings. 

(h) Visits to the reproduction plant by the commander 
and others high in authority are beneficial to the morale 
of personnel, which by virtue of its isolation often needs 
encouragement. 



MAP REPRODUCTION 



137 



19. A. E. F. Issue Schedule of Maps for Infantry Division 

(Based on experience of A. E. F.) 



Div 

Brig 

Regt 

Bn 

Co 

INFANTRY : 

Hq Co 

Sup Co 

Regt (Med Dept and Chap) 

MG Bn (Brig) 

MG Bn (Div) 

MG Co 

Headquarters : 

Div 

Brig 

Regt 

Bn 

MG Bn 

ARTILLERY : 

Brig 

Regt* 

Bn (LA) 

Bn (HvA) 

Btry 

Regt (Med Dept and Chap) 

TM Btry 

Hq Co 

Sup Co 

Headquarters : 

Brig 

Rest 

Bn 

ENGINEERS : 

Regt 

Bn 

Co 

Regt (Med Dept and Chap) 
Headquarters : 

R«gt 

Bn 

SIGNAL CORPS: 

F Sig Bn 

Sup Sec 

Wire Co 

Rad Co , 

Outpost Co 

Hq Bn 

Med Dept and Chap 
DIVISIONAL TRAINS: 

Tn Hq and MP 

Am Tn 

Sup Tn 

Engr Tn 

San Tn 

Mob Ord Rep Sh 



200.000 



251 
55 
24 
5 
1 
2 
1 
3 
5 
8 
1 

24 

2 
1 
1 

61 
18 
5 
4 
1 
8 
1 
1 
1 

4 
8 
2 

17 
5 
1 
2 

5 
2 

7 
1 
1 
1 
1 
2 
1 

6 

11 

4 

2 
6 



80,000 



1,048 

297 

ISO 

35 

8 

7 

7 

2 

81 

17 

7 

S« 
6 
2 
8 
8 

211 

65 

28 

16 

7 

2 

7 

7 

7 

7 
8 
2 

84 
81 
10 

2 

20 

1 

81 
1 
8 
8 
8 
5 
1 

32 

11 

8 

6 

12 

1 



1 


i 


50,000 


20,000 


147 


171 


3 


28 


1 


10 
1 

"~i 

e 

4 
1 

20 


80 


1 


2 


1 


6 
1 
2 

66 


96 


29 


19 


5 


5 


4 


4 


1 


1 


1 


1 


1 


1 


1 


1 


1 


1 


6 





16 


e 


2 


2 


10 


n 


4 


4 


1 


1 
1 


2 


2 


1 


1 


5 


6 


1 


1 


1 


1 


1 


1 


1 


1 


1 


2 

2 
2 


:::: 


1 
1 
1 




10,000 



262 

69 

28 

5 

1 

2 

1 

2 

21 

11 

5 

24 

2 
2 
1 

1 

61 
18 
5 
4 
1 
8 
1 
1 
1 

4 
8 
2 

17 
5 
1 
2 

5 
2 

7 
1 
1 
1 
1 
2 
1 

1 
1 
1 
1 




258 
69 
23 
5 
1 
2 
1 
2 

21 

11 

5. 

24 
2 
2 



61 

18 

5 

4 

1 
8 

1 
1 
1 



17 
8 
1 
2 

8 
8 

7 

1 
1 
1 
1 
2 
1 



•For heavy artillery regiment add one battalion headquarters. 

20. The following is copied from the report of the 
base printing plant at Langres, France, in order to show 
the character and extent of the operations necessary for 
map reproduction on a large scale. 



138 TOPOGRAPHY 

The construction of the base printing plant at Lan- 
gres was started on the arrival of A Company, 29th En- 
gineers, on December 3, 1917. The original construction 
with the expansion, which continued up to the time of the 
armistice as the needs increased and as additional machinery 
was received, was all executed by the 29th Engineers. 

During the construction period a small lithographic 
and type printing plant was established at G. H. Q., for doing 
urgent special work for the General Staff sections. The 
original construction of the base printing plant was com- 
pleted and the plant put in operation June 15, 1918, with a 
drafting room, power plant, one wet plate camera, three 
lithographic presses and a job type printing plant. These 
departments were all planned for an expansion which con- 
tinued up to the tim3 of the armistice. The following ad- 
ditional departments were added: 

Automatic type setting machinery. 
Automatic type printing - machinery. 
Stereotyping plant. 

Photo-engraving and zinc etching plant. 
Book bindery. 

Map, storage and distributing department. 
Graining plant. 

Rapid photographic reproduction plant. 
Machine shop. 

Gas generating plant for relief maps. 

Modeling department for relief maps and 3 large supply 
warehouses. 

At the time of the armistice over fifty machines of 
different types were in operation, occupying 60,000 square 
feet of floor space. The operating force on a 3-shift basis 
totalled 650 ; and about 2i tons of supplies were consumed 
daily. 

The starting of the plant on June 15th was practically 
coincident with the commencement of independent opera- 
tions of American units and consequent demands. It had 
been in operation only two months when it was subjected to 
the severe strain of the St. Mihiel offensive. The original 
order for 140,000 maps was received on August 20th and it 
was apparent that French sources, already overburdened, 
could not be relied on. The operating force at the plant 
was accordingly divided into two 12-hour shifts and operated 
continuously night and day from that time on until the con- 



MAP REPRODUCTION 139 

elusion of the armistice. In addition to a very large num- 
ber of information documents and pamphlets, the total num- 
ber of maps actually printed for the St. Mihiel offensive 
between August 20th and September 9th was 456,000. 

Before this work was completed, it became necessary 
to undertake the printing of maps and documents for the 
Meuse-Argonne operation. The St. Mihiel sector had long 
been indicated as a probable field of operations for Ameri- 
can forces, and the greater part of the necessary plates, 
tracings, and other data for the production of maps had 
been accumulated prior to the announcement of the opera- 
tion ; but the Argonne-Meuse operation was a complete sur- 
prise and great speed was necessary. The system of the 
French Service Geographique required that tracings brought 
up to date should be sent to Paris to be printed, which oc- 
casioned a delay of 4 days. This delay would have been 
fatal to the production in sufficient time for the U.S. Army, 
and in many cases tracings were taken first from the 2d 
French Army Headquarters at Laheycourt to Langres, a 
distance of 168 kilometers, the necessary plates made, and. 
the tracings returned in from 24 to 36 hours' elapsed time.. 
The total number of maps printed for the Meuse-Argonne 
offensive was 747,000. 

At the time of the armistice, the period of trial and 
strain was over. The American Expeditionary Forces were 
independent in map printing and supply, with not only 
a comfortable margin over present needs but with adequate 
provision for future expansion to meet all needs of our 
growing forces. The organization was complete and the 
equipment was the most modern and efficient in France, 
and in the technical processes and plant for reproduction 
of photographic data we were far in advance of French 
plants. 

The total work completed up to November 11th was 
as follows : 

Total number of maps printed 3,134,000 

Total number of documents and pamphlets printed 352,000 

Total number of lithograph impressions 7,000,000 

Total number of type impressions 2,700,000 

After the armistice the plant operated with full force 
on the supply of maps for the 3 armies in the field, reproduc- 



140 TOPOGRAPHY 

ing historical maps and documents in great quantity for 
the records and reports of divisions, corps, armies and G. 
H. Q. Work was carried on during this period on the pre- 
paration of German maps as far east as Berlin, in prepara- 
tion for the possible resumption of hostilities. The equip- 
ment for the printing plant of the 3d Army was collected 
and transferred to Coblenz, and the printing plants of the 
1st and 2d Armies were dismantled and returned to Langres. 
The following is a summary of the work done up to 
May 1, 1919: 

Total number of maps or charts printed 4,357,000 

Total number of documents or pamphlets printed 1,383,000 

Total number of lithographic impressions 11,500,000 

Total number of type impressions 11,000,000 

14,000 reams of paper and 12 tons of ink were used. 



MAP REPRODUCTION 



141 




Figure Tl 




Figure T2 



142 



TOPOGRAPHY 




665 



Figure T3 




Figure T4 



MAP REPRODUCTION 



143 




Figure T5 



144 



TOPOGRAPHY 




Figure T6 
Put in 10-foot contours. 



MAP REPRODUCTION 



670 



860 



6/0 > 



797 




785 



Figure T7 

Scale 1:20,000 

Put in proper contours. 



146 



TOPOGRAPHY 



917 



060 



96Z 



S30 



878 




Put in 20' Contours. 



Figure T8 



MAP REPRODUCTION 



147 



.617 



960 



962 



930 



880 



678 




780 



870 



Figure T9 

Scale: 6" = 1 mile. 
Put in proDer contours. 



148 



TOPOGRAPHY 



930 



640 




Figure T10 

Scale: 1:10,000 

Put in proper contours. 



MAP REPRODUCTION 



149 




-^. soo 



?~> 



Put in 20' Contours. 
Figure Til 



150 



TOPOGRAPHY 



(ogojl 2 




Put in 20-foot contours. 
Figure T12 




760 



Figure T13 



300 
764 




760 



Figure T14 




Figur* T15 



LIBRARY OF CONGRESS 




011 392 990 A 





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